First report of an Ivorian family with nonsyndromic hearing loss caused by GJB2 compound heterozygous variants.

The primary etiology of congenital hearing loss is attributed to genetic factors, with GJB2 identified as a pivotal gene across diverse ethnic groups. Additionally, nonsyndromic hearing loss is predominantly inherited in an autosomal recessive manner. We used Sanger sequencing to analyze GJB2 in 17 deaf children from 13 unrelated Ivory Coast families. One family had two children born with severe congenital deafness and exhibited pathogenic compound heterozygous variants. These variants included a nonsense substitution (c.132G > A or p.Trp44Ter) and a newly discovered duplication of 7 base pairs (c.205_211dupTTCCCCA or p.Ser72ProfsTer32). Segregation testing confirmed these variants, marking the first identification of GJB2 in an Ivorian family with congenital hearing loss.

Cytogenetic and epidemiological profile of chronic myeloid leukemia in Morocco.

Chronic myeloid leukemia (CML) is a neoplastic disease of genetic origin resulting from clonal proliferation of hematopoietic stem cells (HSCs). The reciprocal translocation t(9;22)(q34;q11) is the main chromosomal abnormality involved in this pathology, usually detected by conventional cytogenetics. This article aims to investigate the epidemiological, cytogenetic, therapeutic, and clinical characteristics of Moroccan patients with CML. This research represents the first large-scale study of CML patients in Morocco and was carried out at Institut Pasteur of Morocco. Bone marrow samples were processed for cytogenetic analysis, and karyotypes were described according to an international system of human cytogenetic nomenclature (ISCN 2016). Patients were studied according to their epidemiological characteristics, clinical information and cytogenetic results. For statistical calculations, R version 4.3.1 was used to analyze the data and calculate the statistical parameters. RStudio and Power BI were used for data visualization. The National Cancer Institute (NCI) Surveillance, Epidemiology, and End Results (SEER) method of incidence estimation was used to calculate our incidence. We received 826 patients (from 1992 to 2023) who were referred for suspected CML or who were undergoing treatment. Only 650 patients with confirmed CML were included in the study, all of whom underwent their first cytogenetic test. The median age of our patients was 45 years and the sex ratio was 1.03. At the time of diagnosis, 147 (30%) of the patients had clinical manifestations. Most patients were diagnosed in the chronic phase (94.5%). Nineteen complex variant translocations of the Philadelphia (Ph) chromosome were detected. At the time of diagnosis, 55 (11.5%) patients had ACAs, of which 30 (54.5%) were high-risk ACAs. Based on data from 174 patients treated with imatinib, the median time to complete cytogenetic response (CCyR) was 11 months, and at the last cytogenetic follow-up, 81 patients (46.6%) achieved CCyR, while 64 patients (36.8%) showed no response to treatment. Regarding adherence to European LeukemiaNet (ELN) guidelines, 58 patients (33%) were followed according to these guidelines, with optimal treatment in 8.6%, suboptimal treatment in 7% and treatment failure in 18%. The estimated incidence of chronic myeloid leukemia calculated is 0.6 cases per 100,000 in the Casablanca region. This study provides a detailed overview of CML in Morocco, highlighting important clinical, cytogenetic and therapeutic aspects despite some limitations. It also highlights the need to deepen our understanding of this complex disease for disease management in our specific context.

Impact and prevalence of comorbidities and complications on the severity of COVID-19 in association with age, gender, obesity, and pre-existing smoking: A meta-analysis.

Background: COVID-19 patients usually present multiple comorbidities and complications associated with severe forms of SARS-CoV-2 infection. This study aimed to assess the risk factors and prevalence of comorbidities and complications contributing to the severity of COVID-19. Methods: This meta-analysis was performed according to PRISMA guidelines. We searched various databases, including PubMed, Google Scholar, and Scopus (between 2020 and 2023), for eligible studies for this meta-analysis. Results: Thirty-three studies were eligible, including 85,812 patients, of which 36 % (30,634/85,812) had severe disease, whereas 64 % (55,178/85,812) had non-severe disease. Severe cases were potentially correlated with the following factors: gender (male) (odd ratio (OR) = 1.52, 95 % CI: 1.34-1.73), advanced age (OR = 3.06, 95 % CI: 2.18-4.40) pre-existing smoking (OR = 1.33, 95 % CI: 1.01-1.75), obesity (OR = 2.11, 95 % CI: 1.47-3.04), diabetes (OR = 1.81, 95 % CI: 1.35-2.43), hypertension (OR = 2.22, 95 % CI: 1.72-2.87), coronary heart disease (OR = 2.17, 95 % CI: 1.42-3.31), CKD (OR = 2.27, 95 % CI: 1.26-4.06), COPD (OR = 1.95, 95 % CI: 1.22-3.09), malignancy (OR = 1.63, 95 % CI: 1.07-2.49) and cerebrovascular disease (OR = 2.76, 95 % CI: 1.63-4.62). All these comorbidities were significantly higher in the severe COVID-19 group compared with the non-severe COVID-19 group. In addition, the most severe complications were associated with shock (OR = 28.08, 95 % CI: 3.49-226.03), ARDS (OR = 13.09, 95 % CI: 5.87-29.18), AKI (OR = 16.91, 95 % CI: 1.87-152.45) and arrhythmia (OR = 7.47, 95 % CI: 2.96-18.83). However, these complications were the most likely to prevent recovery in patients with severe affections compared with non-severe affection groups. Conclusion: All the comorbidities and complications listed above are more likely to cause severe forms of COVID-19 in some patients and hinder recovery. They are therefore risk factors to be controlled to minimize the undesirable effects of the disease.

Analysis and Risk Assessment of Essential and Toxic Elements in Algerian Canned Tuna Fish.

In Algeria, the data and research on the essential and toxic chemical elements in food are limited and insufficient; therefore, the present study focused on evaluating the essential and toxic elements content in different 11 brands with two types (tomato and oil) of canned tuna fish, consumed in Algeria in 2022, by inductively coupled plasma-optical emission spectrometer (ICP-OES), while mercury (Hg) levels were determined by cold vapor atomic absorption spectrophotometry, as well as estimate the probabilistic risk assessment. The elements in canned tuna fish commercialized for human consumption in Algeria were determined by ICP-OES methods, The results showed that the heavy metal concentration in the samples under study ranged from 49.11 to 289.80 mg.kg-1 (Ca), 0.0045 to 0.2598 mg.kg-1 (Cd), 0.128 to 1.21 mg.kg-1 (Cr), 8.55 to 35.94 mg.kg-1 (Fe), 121.27 to 379.17 mg.kg-1 (Mg), 0.0767 to 1.2928 mg.kg-1 (Mn), 2.10 to 3.95 mg.kg-1 (Mo), and 2.86 to 35.90 mg.kg-1 (Zn), whereas Cu, Pb, Cu, Ni, and As were under limit of detection (LOD), while the toxic elements of mercury (Hg) levels were determined by cold vapor atomic absorption spectrophotometry which showed a content ranged from 0.0186 to 0.0996 mg.kg-1. The levels of mineral elements concentration were close to the minimum recommended by Food and Agriculture Organization (FAO). Obtained data for this investigation can be suitable for Algerian food purposes.

Evaluation of SARS-CoV-2 infection risks after primary vaccination with BNT162b2, BBIBP-CorV, or ChAdOx1-nCOV-19 and after homologous and heterologous booster vaccinations with these vaccines and evaluation of SARS-CoV-2 reinfection profiles.

Background: The emergence of SARS-CoV-2 variants has significantly increased the number of cases of COVID-19 among vaccinated individuals, raising concerns about the effectiveness of current vaccines. The aim of this study was to analyze the SARS-CoV-2 infection risks after primary vaccination with BNT162b2, BBIBP-CorV, or ChAdOx1-nCOV-19 and after homologues and heterologous booster vaccinations with these vaccines, as well as the profiles of reinfected patients. Methods: We analyzed retrospectively 1082 patients vaccinated or unvaccinated with BNT162b2, BBIBP-CorV, and/or ChAdOx1nCoV-19 vaccines to determine their SARS-CoV2 infection statuses using the reverse transcription-polymerase chain reaction (RT-PCR) in addition to their clinical features. The infection risks of patients receiving the different vaccine regimens were compared using multivariate logistic regression analysis, comparing the adjusted OR of a positive COVID-19 test result. Results: Among 596 vaccinated patients, 53%(n = 286) tested positive for SARS-CoV-2 and 57%(n = 310) tested negative. Among positive cases, 10 were reinfection cases. The risk of SARS-CoV-2 infection was 1.6 (adj. OR) for patients who received one dose compared with those who received two doses (95% CI = 1.3-1.8; p < 0.01).The risk was 2.6 (adj. OR) for patients who received one dose compared with those who received three doses (95%CI = 2.1-3.3; p < 0.01), and 1.6 (adj. OR) for patients who received two doses compared with those who received three doses (95% CI = 1.3-2; p < 0.01). The patients who received two doses that were heterologous to that of the primary vaccine had the lowest risk of infection. Booster vaccinations (third dose) significantly reduced the number of positive cases with an acceptable safety profile. Higher cycle-threshold (Ct) values (indicative of viral load) were observed in vaccinated patients, whereas low Ct values were observed in unvaccinated patients. Conclusion: A complete cycle of vaccination with homologous vaccines or heterologous vaccines resulted in an acceptable reduction in SARS-CoV-2 infection. Further, vaccination was associated with a reduction in viral load.

Exploring the impact of CYP11A1's missense SNPs on the interaction between CYP11A1 and cholesterol: A comprehensive structural analysis and MD simulation study.

The process of steroidogenesis plays a vital role in human physiology as it governs the biosynthesis of mineralocorticoids, glucocorticoids, and androgens. These three classes of steroid hormones are primarily produced in the adrenal and gonadal glands through steroidogenesis pathways. Initiated by the side chain cleavage of cholesterol (CLR), this process leads to the conversion of cholesterol into pregnenolone and isocaproic aldehyde. The enzyme CYP11A1, encoded by the CYP11A1 gene, plays a key role in catalyzing the side chain cleavage of CLR. Several single nucleotide polymorphisms (SNPs) have been identified in the CYP11A1 gene, which may predispose carriers to disorders associated with abnormal steroidogenesis. Specifically, missense SNPs in the CYP11A1 gene have the potential to negatively impact the interaction between CYP11A1 and CLR, thus affecting the overall metabolome of steroid hormones. In this computational study, we focused on a specific set of missense SNPs reported in the CYP11A1 gene, aiming to identify variants that directly impact the interaction between CYP11A1 and CLR. The three-dimensional structure of the CYP11A1-CLR complex was obtained from the RCSB Protein Data Bank, while missense SNPs in the CYP11A1 gene were retrieved from Ensembl. To predict the most deleterious variants, we utilized the ConSurf server, SIFT, and PolyPhen. Furthermore, we assessed the impact of induced amino acid (AA) substitutions on the CYP11A1-CLR interaction using the PRODIGY server, PyMol, and Ligplot programs. Additionally, molecular dynamics (MD) simulations were conducted to analyze the effects of deleterious variants on the structural dynamics of the CYP11A1-CLR complex. Among the 8096 retrieved variants, we identified ten missense SNPs (E91K, W147G, R151W, R151Q, S391C, V392M, Q395K, Q416E, R460W, and R460Q) as deleterious for the interaction between CYP11A1 and CLR. MD simulations of the CYP11A1-CLR complexes carrying these deleterious AA substitutions revealed that Q416E, W147G, R460Q, and R460W had the most pronounced impacts on the structural dynamics of the complex. Consequently, these missense SNPs were considered the most deleterious ones. Further functional tests are recommended to assess the impact of these four missense SNPs on the enzymatic activity of CYP11A1. Moreover, Genome-Wide Association Studies (GWAS) should be conducted to determine the significance of their association with abnormal steroidogenesis diseases in various patient groups.

Epidemiology, clinical characteristics and risk factors of coronavirus disease 2019 (COVID-19) in Casablanca.

This is an analytical cross-sectional study of coronavirus disease 2019 (COVID-19) based on data collected between 1 November 2020 and 31 March 2021 in Casablanca focusing on the disease's epidemiological status and risk factors. A total of 4569 samples were collected and analysed by reverse-transcription polymerase chain reaction (RT-PCR); 967 patients were positive, representing a prevalence of 21.2 % for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The mean age was 47.5±18 years, and infection was more common in young adults (<60 years). However, all age groups were at risk of COVID-19, and in terms of disease severity, the elderly were at greater risk because of potential underlying health problems. Among the clinical signs reported in this study, loss of taste and/or smell, fever, cough and fatigue were highly significant predictors of a positive COVID-19 test result (P<0.001). An assessment of the reported symptoms revealed that 27 % of COVID-19-positive patients (n=261) experienced loss of taste and/or smell, whereas only 2 % (n=72) of COVID-19-negative patients did (P<0.001). This result was consistent between univariate (OR=18.125) and multivariate (adjusted OR=10.484) logistic regression analyses, indicating that loss of taste and/or smell is associated with a more than 10-fold higher multivariate adjusted probability of a positive COVID-19 test (adjusted OR=10.48; P<0.001). Binary logistic regression model analysis based on clinical signs revealed that loss of taste and/or smell had a performance index of 0.846 with a P<0.001, confirming the diagnostic utility of this symptom for the prediction of COVID-19-positive status. In conclusion, symptom evaluation and a RT-PCR [taking into account cycle threshold (C t) values of the PCR proxy] test remain the most useful screening tools for diagnosing COVID-19. However, loss of taste/smell, fatigue, fever and cough remain the strongest independent predictors of a positive COVID-19 result.

Computational study of the potential impact of AURKC missense SNPs on AURKC-INCENP interaction and their correlation to macrozoospermia.

Aurora Kinase C (AURKC) is considered an important element in Chromosome Passenger Complex (CPC), its interaction with Inner Centromere Protein (INCENP) plays a critical role in the establishment and the recruitment of a stable CPC during spermatogenesis. Genetic variations of AURKC gene are susceptible to impact AURKC-INCENP interaction, which may affect CPC stability and predispose male subjects to macrozoospermia. In this study, we systematically applied computational approaches using different bioinformatic tools to predict the effect of missense SNPs reported on AURKC gene, we selected the deleterious ones and we introduced their corresponding amino acid substitutions on AURKC protein structure. Then we did a protein-protein docking between AURKC variants and INCENP followed by a structural assessment of each resulting complex using PRODIGY server, Yassara view, Ligplot + and we choose the complexes of the most impactful variants for molecular dynamics (MD) simulation study. Seventeen missense SNPs of AURKC were identified as deleterious between all reported ones. All of them were located on relatively conserved positions on AURKC protein according to Consurf server. Only the four missense SNPs; E91K, D166V, D221Y and G235V were ranked as the most impactful ones and were chosen for MD simulation. D221Y and G235V were responsible for the most remarkable changes on AURKC-INCENP structural stability, therefore, they were selected as the most deleterious ones. Experimental studies are recommended to test the actual effect of these two variants and their actual impact on the morphology of sperm cells.Communicated by Ramaswamy H. Sarma.

A Novel Homozygous Missense Mutation in the FU-CRD2 Domain of the R-spondin1 Gene Associated with Familial 46,XX DSD.

R-spondin proteins are secreted agonists of canonical WNT/ß-catenin signaling. Homozygous RSPO1 mutations cause a syndrome of 46,XX disorder of sexual development (DSD), palmoplantar keratoderma (PPK), and predisposition to squamous cell carcinoma. We report exome sequencing data of two 46,XX siblings, one with testicular DSD and the other with suspected ovotesticular DSD. Both have PPK and hearing impairment and carried a novel homozygous mutation c.332G>A (p.Cys111Tyr) located in the highly conserved furin-like cysteine-rich domain-2 (FU-CRD2). Cysteines in the FU-CRDs are strictly conserved, indicating their functional importance in WNT signaling through interaction with the leucine-rich repeat-containing G-protein-coupled receptors. This is the first RSPO1 missense mutation reported in association with human disease.

Chromosomal abnormalities and Y chromosome microdeletions in infertile men from Morocco.

BACKGROUND: Male infertility is responsible for 50% of infertile couples. Thirty percent of male infertility is due to cytogenetic and genetic abnormalities. In Arab and North African populations, several studies have shown the association of these chromosomal abnormalities with male infertility. Our objective is to evaluate the frequency of chromosomal abnormalities and Y chromosome microdeletions in infertile men from Morocco. METHODS: A total of 573 Moroccan infertile men (444 azoospermic and 129 oligozoospermic men) referred for cytogenetic analysis to the Department of Cytogenetics of the Pasteur Institute of Morocco, were screened for the presence of chromosomal abnormalities and Y chromosome microdeletions. RESULTS: Chromosomal abnormalities accounted for approximately 10.5% (60/573). Fifty six cases among them have sex chromosome abnormalities (93.34%), including Klinefelter's syndrome in 41 patients (68.34%). Autosomal chromosome abnormalities (6.66%) were observed in 4 patients. Chromosomal abnormalities were more prevalent in azoospermic men (13.06%) than in oligospermic men (1.55%). Y microdeletions were detected in 16 of 85 patients (AZFc: 14.12%, AZFbc: 4.70%), most of them where azoospermic men with no chromosomal abnormality. CONCLUSIONS: These results highlighted the need for efficient molecular genetic testing in male infertility diagnosis. In addition, a genetic screening should be performed in infertile men before starting assisted reproductive treatments.

YajL, the prokaryotic homolog of the Parkinsonism-associated protein DJ-1, protects cells against protein sulfenylation.

YajL is the closest Escherichia coli homolog of the Parkinsonism-associated protein DJ-1, a multifunctional oxidative stress response protein whose biochemical function remains unclear. We recently described the oxidative-stress-dependent aggregation of proteins in yajL mutants and the oxidative-stress-dependent formation of mixed disulfides between YajL and members of the thiol proteome. We report here that yajL mutants display increased protein sulfenic acids levels and that formation of mixed disulfides between YajL and its protein substrates in vivo is inhibited by the sulfenic acid reactant dimedone, suggesting that YajL preferentially forms disulfides with sulfenylated proteins. YajL (but not YajL(C106A)) also forms mixed disulfides in vitro with the sulfenylated form of bovine serum albumin. The YajL-serum albumin disulfides can be subsequently reduced by glutathione or dihydrolipoic acid. We also show that DJ-1 can form mixed disulfides with sulfenylated E. coli proteins and with sulfenylated serum albumin. These results suggest that YajL and possibly DJ-1 function as covalent chaperones involved in the detection of sulfenylated proteins by forming mixed disulfides with them and that these disulfides are subsequently reduced by low-molecular-weight thiols.

YajL, prokaryotic homolog of parkinsonism-associated protein DJ-1, functions as a covalent chaperone for thiol proteome.

YajL is the closest Escherichia coli homolog of the Parkinsonism-associated protein DJ-1, a multifunctional oxidative stress response protein whose biochemical function remains unclear. We recently reported the aggregation of proteins in a yajL mutant in an oxidative stress-dependent manner and that YajL exhibits chaperone activity. Here, we show that YajL displays covalent chaperone and weak protein oxidoreductase activities that are dependent on its exposed cysteine 106. It catalyzes reduced RNase oxidation and scrambled RNase isomerization and insulin reduction and forms mixed disulfides with many cellular proteins upon oxidative stress. The formation of mixed disulfides was detected by immunoblotting bacterial extracts with anti-YajL antibodies under nonreducing conditions. Disulfides were purified from bacterial extracts on a YajL affinity column, separated by nonreducing-reducing SDS-PAGE, and identified by mass spectrometry. Covalent YajL substrates included ribosomal proteins, aminoacyl-tRNA synthetases, chaperones, catalases, peroxidases, and other proteins containing cysteines essential for catalysis or FeS cluster binding, such as glyceraldehyde-3-phosphate dehydrogenase, aldehyde dehydrogenase, aconitase, and FeS cluster-containing subunits of respiratory chains. In addition, we show that DJ-1 also forms mixed disulfides with cytoplasmic proteins upon oxidative stress. These results shed light on the oxidative stress-dependent chaperone function of YajL and identify YajL substrates involved in translation, stress protection, protein solubilization, and metabolism. They reveal a crucial role for cysteine 106 and suggest that DJ-1 also functions as a covalent chaperone. These findings are consistent with several defects observed in yajL or DJ-1 mutants, including translational defects, protein aggregation, oxidative stress sensitivity, and metabolic deficiencies.

Translational defects in a mutant deficient in YajL, the bacterial homolog of the parkinsonism-associated protein DJ-1.

We report here that YajL is associated with ribosomes and interacts with many ribosomal proteins and that a yajL mutant of Escherichia coli displays decreased translation accuracy, as well as increased dissociation of 70S ribosomes into 50S and 30S subunits after oxidative stress.

Protein aggregation in a mutant deficient in yajL, the bacterial homolog of the Parkinsonism-associated protein DJ-1.

YajL is the closest prokaryotic homolog of the parkinsonism-associated protein DJ-1 (40% sequence identity and similar three-dimensional structure), a protein of unknown function involved in the cellular response to oxidative stress. We report here that a yajL mutant of Escherichia coli displays an increased sensitivity to oxidative stress. It also exhibits a protein aggregation phenotype in aerobiosis, but not in anaerobiosis or in aerobic cells overexpressing superoxide dismutase, suggesting that protein aggregation depends on the presence of reactive oxygen species produced by respiratory chains. The protein aggregation phenotype of the yajL mutant, which can be rescued by the wild-type yajL gene, but not by the corresponding cysteine 106 mutant allele, is similar to that of multiple mutants deficient in superoxide dismutases and catalases, although intracellular hydrogen peroxide levels were not increased in the yajL mutant, suggesting that protein aggregation in this strain does not result from a hydrogen peroxide detoxification defect. Aggregation-prone proteins included 17 ribosomal proteins, the ATP synthase beta subunit, flagellin, and the outer membrane proteins OmpA and PAL; all of them are part of multiprotein complexes, suggesting that YajL might be involved in optimal expression of these complexes, especially during oxidative stress. YajL stimulated the renaturation of urea-unfolded citrate synthase and the solubilization of the urea-unfolded ribosomal proteins S1 and L3 and was more efficient as a chaperone in its oxidized form than in its reduced form. The mRNA levels of several aggregated proteins of the yajL mutant were severely affected, suggesting that YajL also acts at the level of gene expression. These two functions of YajL might explain the protein aggregation phenotype of the yajL mutant.

Membrane docking of an aggregation-prone protein improves its solubilization.

We used preS2-S'-beta-galactosidase, a three domain fusion protein that aggregates extensively at 43 degrees C in the cytoplasm of Escherichia coli to search for multicopy suppressors of protein aggregation and inclusion bodies formation, and took advantage of the known differential solubility of preS2-S'-beta-galactosidase at 37 and 43 degrees C to develop a selection procedure for the gene products that would prevent its aggregation in vivo at 43 degrees C. First, we demonstrate that the differential solubility of preS2-S'-beta-galactosidase results in a lactose-positive phenotype at 37 degrees C as opposed to a lactose-negative phenotype at 43 degrees C. We searched for multicopy suppressors of preS2-S'-beta-galactosidase aggregation at 43 degrees C by selecting pink lactose-positive colonies on a background of white lactose-negative colonies after transformation of bacteria with an E. coli gene bank. We found only two multicopy suppressors of preS2-S'-beta-galactosidase aggregation at 43 degrees C, protein isoaspartate methyltransferase (PIMT) and the membrane components ChbBC of the N,N'-diacetylchitobiose phosphotransferase transporter. We have previously shown that PIMT overexpression reduces the level of isoaspartate in preS2-S'-beta-galactosidase, increases its thermal stability and consequently helps in its solubilization at 43 degrees C (Kern et al., J. Bacteriol. 187, 1377-1383). In the present work, we show that ChbBC overexpression targets a fraction of preS2-S'-beta-galactosidase to the membrane, and decreases its amount in inclusion bodies, which results in its decreased thermodenaturation and in a lactose-positive phenotype at 43 degrees C. Cross-linking experiments show that the inner membrane protein ChbC interacts with preS2-S'-beta-galactosidase. Our results suggest that membrane docking of aggregation-prone proteins might be a useful method for their solubilization.

The thioredoxin homolog YbbN functions as a chaperone rather than as an oxidoreductase.

Escherichia coli contains two thioredoxins, Trx1 and Trx2, and a thioredoxin-like protein, YbbN, which presents a strong homology in its N-terminal part with thioredoxins, and possesses a 20kDa C-terminal part of unknown function. We reported previously that YbbN displays both protein oxido-reductase and chaperone properties in vitro. In this study, we show that an ybbN-deficient strain displays an increased sensitivity to thermal stress but not to oxidative stress, a normal redox state of its cellular proteins but a decreased expression of several cytoplasmic proteins, including EF-Tu, DnaK, GroEL, trigger factor and several Krebs cycle enzymes, suggesting that the chaperone properties of YbbN are more important in vivo than its redox properties. YbbN specifically interacts with DnaK and GroEL, as shown by reverse purification. It increases 4-fold the rate of protein renaturation in vitro by the DnaK chaperone machine, suggesting that it cooperates with DnaK for the optimal expression of several cytoplasmic proteins.

Solubilization of protein aggregates by the acid stress chaperones HdeA and HdeB.

The acid stress chaperones HdeA and HdeB of Escherichia coli prevent the aggregation of periplasmic proteins at acidic pH. We show in this report that they also form mixed aggregates with proteins that have failed to be solubilized at acidic pH and allow their subsequent solubilization at neutral pH. HdeA, HdeB, and HdeA and HdeB together display an increasing efficiency for the solubilization of protein aggregates at pH 3. They are less efficient for the solubilization of aggregates at pH 2, whereas HdeB is the most efficient. Increasing amounts of periplasmic proteins draw increasing amounts of chaperone into pellets, suggesting that chaperones co-aggregate with their substrate proteins. We observed a decrease in the size of protein aggregates in the presence of HdeA and HdeB, from very high molecular mass aggregates to 100-5000-kDa species. Moreover, a marked decrease in the exposed hydrophobicity of aggregated proteins in the presence of HdeA and HdeB was revealed by 1,1'-bis(4-anilino)naphtalene-5,5'-disulfonic acid binding experiments. In vivo, during the recovery at neutral pH of acid stressed bacterial cells, HdeA and HdeB allow the solubilization and renaturation of protein aggregates, including those formed by the maltose receptor MalE, the oligopeptide receptor OppA, and the histidine receptor HisJ. Thus, HdeA and HdeB not only help to maintain proteins in a soluble state during acid treatment, as previously reported, but also assist, both in vitro and in vivo, in the solubilization at neutral pH of mixed protein-chaperone aggregates formed at acidic pH, by decreasing the size of protein aggregates and the exposed hydrophobicity of aggregated proteins.

Escherichia coli HdeB is an acid stress chaperone.

We cloned, expressed, and purified the hdeB gene product, which belongs to the hdeAB acid stress operon. We extracted HdeB from bacteria by the osmotic-shock procedure and purified it to homogeneity by ion-exchange chromatography and hydroxyapatite chromatography. Its identity was confirmed by mass spectrometry analysis. HdeB has a molecular mass of 10 kDa in sodium dodecyl sulfate-polyacrylamide gel electrophoresis, which matches its expected molecular mass. We purified the acid stress chaperone HdeA in parallel in order to compare the two chaperones. The hdeA and hdeB mutants both display reduced viability upon acid stress, and only the HdeA/HdeB expression plasmid can restore their viability to close to the wild-type level, suggesting that both proteins are required for optimal protection of the bacterial periplasm against acid stress. Periplasmic extracts from both mutants aggregate at acidic pH, suggesting that HdeA and HdeB are required for protein solubilization. At pH 2, the aggregation of periplasmic extracts is prevented by the addition of HdeA, as previously reported, but is only slightly reduced by HdeB. At pH 3, however, HdeB is more efficient than HdeA in preventing periplasmic-protein aggregation. The solubilization of several model substrate proteins at acidic pH supports the hypothesis that, in vitro, HdeA plays a major role in protein solubilization at pH 2 and that both proteins are involved in protein solubilization at pH 3. Like HdeA, HdeB exposes hydrophobic surfaces at acidic pH, in accordance with the appearance of its chaperone properties at acidic pH. HdeB, like HdeA, dissociates from dimers at neutral pH into monomers at acidic pHs, but its dissociation is complete at pH 3 whereas that of HdeA is complete at a more acidic pH. Thus, we can conclude that Escherichia coli possesses two acid stress chaperones that prevent periplasmic-protein aggregation at acidic pH.

The Escherichia coli thioredoxin homolog YbbN/Trxsc is a chaperone and a weak protein oxidoreductase.

Escherichia coli contains two thioredoxins, Trx1 and Trx2, and a thioredoxin-like protein, YbbN, which presents a strong homology in its N-terminal part with thioredoxin 1 and 2. YbbN, however, does not possess the canonical Cys-x-x-Cys active site of thioredoxins, but instead a Ser-x-x-Cys site. In addition to Cys-38, located in the SxxC site, it contains a second cysteine, Cys-63, close to Cys-38 in the 3D model. Cys-38 and Cys-63 undergo an oxidoreduction process, suggesting that YbbN functions with two redox cysteines. Accordingly, YbbN catalyzes the oxidation of reduced RNase and the isomerization of scrambled RNase. Moreover, upon oxidation, its oligomeric state changes from dimers to tetramers and higher oligomers. YbbN also possesses chaperone properties, promoting protein folding after urea denaturation and forming complexes with unfolded proteins. This is the first biochemical characterization of a member of the YbbN class of bacterial thioredoxin-like proteins, and in vivo experiments will allow to determine the importance of its redox and chaperone properties in the cellular physiology.

Cloning, expression, and purification of the general stress protein YhbO from Escherichia coli.

We cloned, expressed, and purified the Escherichia coli yhbO gene product, which is an amino acid sequence homolog to the Bacillus subtilis general stress protein 18 (the yfkM gene product), the Pyrococcus furiosus intracellular protease PfpI, and the human Parkinson disease protein DJ-1. The gene coding for YhbO was generated by amplifying the yhbO gene from E. coli by polymerase chain reaction. It was inserted into the expression plasmid pET-21a, under the transcriptional control of the bacteriophage T7 promoter and lac operator. A BL21 (DE3) E. coli strain transformed with the YhbO-expression vector, pET-21a-yhbO, accumulates large amounts of a soluble protein with a molecular mass of 20 kDa in SDS-PAGE that matches the expected YhbO molecular weight. YhbO was purified to homogeneity by ion exchange chromatography and hydroxyapatite chromatography, and its identity was confirmed by N-terminal sequencing and mass spectrometry analysis. The native protein exists in monomeric, trimeric, and hexameric forms. We also report a strong sequence homology between YhbO and the general stress protein YfkM (64% identities), which suggests that YhbO is a stress protein, and a strong structural homology between YhbO and the Pyrococcus horikoshii intracellular protease PhpI. We could not, however, detect any proteolytic or peptidolytic activity of YhbO, using classical biochemical substrates.