Prevalence of hepatitis B and C infections among HIV-positive men who have sex with men: A systematic review and meta-analysis.

Background: Human immunodeficiency virus (HIV) infection is highly prevalent and often coexists with other infectious diseases, especially Hepatitis B virus (HBV) and Hepatitis C virus (HCV). Men who have sex with men (MSM) represent a vulnerable population in terms of HIV infection. We aimed to determine the prevalence of HCV, HBV among HIV-infected MSM. Methods: This systematic review and meta-analysis searched PubMed, Cochrane, Scopus, Web of Science, and ProQuest up-to 2023/04/22. All studies reporting the prevalence of HBV or HCV infection in MSM PLHIV were included. Meta-analysis used random effect model for synthesis and I 2 along with prediction interval for heterogeneity. Subgroup analysis based on continent and meta-regression for study size, average age and year of publication were used to explore heterogeneity. Modified Newcastle-Ottawa Scale was used to evaluate the quality of studies according to the protocol (PROSPERO: CRD42023428764). Results: Fifty-six of 5948 studies are included. In 53 studies with 3,07,589 participants, a pooled prevalence of 7% (95% confidence interval [CI]: 5-10) was found for HCV among MSM PLHIV, while a 9% (95% CI: 4-18) prevalence was found for HBV infection from five studies which included 5641 MSM PLHIV. Asia reported the lowest pooled prevalence at 5.84% (95% CI: 2.98-11.13) for HCV while Europe reported the highest pooled prevalence at 7.76% (95% CI: 4.35-13.45). Baujat plot and influence diagnostic identified contributors to influence and between-study heterogeneity. Sensitivity analyses omitting these studies result in considerably more precise estimates. Another sensitivity analysis as leave-one-out meta-analysis did not change any pooled estimate significantly. Conclusion: There is a significant burden of HCV and HBV among MSM PLHIV worldwide, with varying prevalence rates. Future studies should focus on these multimorbidity clusters and investigate factors influencing disease burden, long-term outcomes, optimal testing strategies, and tailored interventions.

Efficacy of stem cell therapy in patients with chronic liver disease: an umbrella review of systematic reviews.

BACKGROUND: Stem cell therapy offers promising benefits like modulating immune responses, reducing inflammation, and aiding liver regeneration. This umbrella review seeks to compile evidence from systematic reviews to assess the efficacy of stem cell therapy for improving liver function and survival rates in chronic liver disease patients. METHODS: We searched electronic databases up to February 15, 2024. The selection process focused on systematic reviews comparing stem cell therapy with standard care or a placebo. The primary outcomes evaluated were changes in liver enzymes, the MELD score, and survival rates. Nested Knowledge software was utilized for screening and data extraction. All statistical analyses were performed using R software, version 4.3. RESULTS: Our umbrella review included 28 systematic reviews. The meta-analysis showcased a notable improvement in survival rates with a pooled RR of 1.487 (95% CI: 1.281 to 1.727). In non-randomized studies, albumin levels exhibited an SMD of 0.786 (95% CI: 0.368 to 1.204), indicating positive therapeutic effects. For ALT, the meta-analysis revealed a decrease in levels with an SMD of -0.499 (95% CI: -0.834 to -0.164), and for AST, an overall SMD of -0.362 (95% CI: -0.659 to -0.066) was observed, suggesting hepatoprotective effects. No significant changes were observed in total bilirubin levels and MELD scores in RCTs. CONCLUSION: Stem cell therapy exhibits potential as a novel treatment for chronic liver diseases, as it has demonstrated improvements in survival rates and certain liver function markers. More high-quality RCTs are needed in the future to fully ascertain the efficacy of stem cell therapy in this patient population.

Antioxidant Genes Variants and Their Association with Sperm DNA Fragmentation.

Semen possesses a variety of antioxidant defense mechanisms which protect sperm DNA from the damaging effects of oxidative stress. Correlation between antioxidant genes variants and sperm DNA fragmentation (SDF) level is not sufficiently studied. Therefore, we investigated the association between several single nucleotide polymorphisms (SNPs): CYP1A1 (rs1048943A > G), CYP4F2 (rs2108622G > A), NRF2 (rs6721961C > A), PON1 (rs662A > G), NOS3 (rs1799983G > T), GSTM1 (null), CAT (rs1001179C > T), SOD2 (rs4880A > G), GSTP1 (rs1695A > G), PON2 (rs7493G > C), EPHX2 (rs1042064T > C), and AHR (rs2066853G > A) and elevated SDF. The study employed a case-control design where, the allele and genotype frequencies of the selected SNPs were compared between 75 semen samples with abnormal SDF (the cases) and 75 samples with normal SDF (the controls). DNA was extracted from the semen samples and allele-specific PCR (AS-PCR) was used for genotyping the SNPs. Relevant data were collected from the patients' records et al.-Basma Fertility Center. Suitable statistical tests and multifactorial dimensionality reduction (MDR) test were used to anticipate SNP-SNP interactions. Comparison of semen parameters revealed significant differences between cases and controls in terms of liquefaction time, sperm total motility, and normal form. Genotype frequencies of NOS3 G > T (GT), SOD2 A > G (AA and AG), EPHX2 T > C (CC and CT), and AHR G > A (GA and GG) were significantly different between cases and controls. Allele frequencies of SOD2 (G-allele), and EPHX2 (T-allele) also significantly varied between cases and controls. MDR analysis revealed that the NOS3, SOD2, and EPHX2 SNPs combination has the highest impact on SDF. The study findings suggest that genetic variations in genes involved antioxidant defenses contribute to abnormal SDF.

ARID5B, IKZF1, GATA3, CEBPE, and CDKN2A germline polymorphisms and predisposition to childhood acute lymphoblastic leukemia.

Acute lymphoblastic leukemia (ALL) is the most frequent type of pediatric cancer. Germline single nucleotide polymorphisms (SNPs), including ARID5B (rs10821936 T/C), IKZF1 (rs4132601 T/G), GATA3 (rs3824662 G/T), CEBPE (rs2239633 G/A), and CDKN2A (rs3731217 A/C) have been linked to pediatric ALL in different populations. Hitherto, no previous studies have tested the relationship between these SNPs and pediatric ALL in Gaza strip. Therefore, we investigated the association between these polymorphisms and the occurrence of childhood ALL in this part of Palestine. This case-control study recruited 100 healthy controls and 78 ALL patients. Allele-specific PCR (AS-PCR) technique was used for SNPs genotyping. Relevant statistical tests were used and the multifactor dimensionality reduction (MDR) approach was applied in the analysis of gene-gene interactions. Minor alleles of ARID5B rs10821936 T/C (p = 0.007) and IKZF1 rs4132601 T/G (p = 0.045) were significantly higher in ALL patients. The homozygous (TT) genotype of GATA3 rs3824662 G/T (p = 0.038), (CC) of ARID5B rs10821936 T/C (p = 0.008), and (AC and CC) genotypes of CDKN2A rs3731217 A/C (p < 0.0001) were significantly higher in ALL cases. On MDR analysis, the best model for ALL risk was the five-factor model combination of the examined SNPs (CVC = 10/10; TBA = 0.632; p < 0.0001). This work demonstrates the association of ARID5B rs10821936 T/C, IKZF1 rs4132601 T/G, GATA3 rs3824662 G/T, and CDKN2A rs3731217 A/C polymorphisms with increased risk of pediatric ALL among a patient cohort from Gaza Strip. Further studies with a larger sample size are needed in order to confirm these findings and test the value of these SNPs in prognosis and treatment sensitivity.

Exploration of the physical states of riboflavin (free base) by mechanical milling.

Amorphous riboflavin (free base) could be produced for the first time via high energy ball milling of a commercial crystalline form (Form I). Importantly, this solid state amorphization process allowed to circumvent chemical degradation occurring during melting as well as the lack of suitable solvents, which are required for amorphization via spray- or freeze-drying. The amorphous state of riboflavin was thoroughly characterized, revealing a complex recrystallization pattern upon heating, involving two enantiotropic polymorphic forms (II and III) and a dihydrate. The glass transition temperature (Tg) and heat capacity (Cp) jump of the amorphous form were determined as 144 °C and 0.68 J/g/°C. Moreover, the relative physical stability of the different physical states has been elucidated, e.g., at room temperature: I > II > III. The following rank order was observed for the dissolution rates in water at 37 °C during the first 4 h: amorphous > III ≈ II > I. Afterwards, a dihydrate crystallized from the solutions of amorphous and metastable crystalline riboflavin forms, the solubility of which was well above the solubility of the stable FormI.

Structure of Geobacter cytochrome OmcZ identifies mechanism of nanowire assembly and conductivity.

OmcZ nanowires produced by Geobacter species have high electron conductivity (>30 S cm-1). Of 111 cytochromes present in G. sulfurreducens, OmcZ is the only known nanowire-forming cytochrome essential for the formation of high-current-density biofilms that require long-distance (>10 µm) extracellular electron transport. However, the mechanisms underlying OmcZ nanowire assembly and high conductivity are unknown. Here we report a 3.5-Å-resolution cryogenic electron microscopy structure for OmcZ nanowires. Our structure reveals linear and closely stacked haems that may account for conductivity. Surface-exposed haems and charge interactions explain how OmcZ nanowires bind to diverse extracellular electron acceptors and how organization of nanowire network re-arranges in different biochemical environments. In vitro studies explain how G. sulfurreducens employ a serine protease to control the assembly of OmcZ monomers into nanowires. We find that both OmcZ and serine protease are widespread in environmentally important bacteria and archaea, thus establishing a prevalence of nanowire biogenesis across diverse species and environments.

Structure of the bacterial flagellar hook cap provides insights into a hook assembly mechanism.

Assembly of bacterial flagellar hook requires FlgD, a protein known to form the hook cap. Symmetry mismatch between the hook and the hook cap is believed to drive efficient assembly of the hook in a way similar to the filament cap helping filament assembly. However, the hook cap dependent mechanism of hook assembly has remained poorly understood. Here, we report the crystal structure of the hook cap composed of five subunits of FlgD from Salmonella enterica at 3.3 Å resolution. The pentameric structure of the hook cap is divided into two parts: a stalk region composed of five N-terminal domains; and a petal region containing five C-terminal domains. Biochemical and genetic analyses show that the N-terminal domains of the hook cap is essential for the hook-capping function, and the structure now clearly reveals why. A plausible hook assembly mechanism promoted by the hook cap is proposed based on the structure.

Structure of Geobacter pili reveals secretory rather than nanowire behaviour.

Extracellular electron transfer by Geobacter species through surface appendages known as microbial nanowires1 is important in a range of globally important environmental phenomena2, as well as for applications in bio-remediation, bioenergy, biofuels and bioelectronics. Since 2005, these nanowires have been thought to be type 4 pili composed solely of the PilA-N protein1. However, previous structural analyses have demonstrated that, during extracellular electron transfer, cells do not produce pili but rather nanowires made up of the cytochromes OmcS2,3 and OmcZ4. Here we show that Geobacter sulfurreducens binds PilA-N to PilA-C to assemble heterodimeric pili, which remain periplasmic under nanowire-producing conditions that require extracellular electron transfer5. Cryo-electron microscopy revealed that C-terminal residues of PilA-N stabilize its copolymerization with PilA-C (to form PilA-N-C) through electrostatic and hydrophobic interactions that position PilA-C along the outer surface of the filament. PilA-N-C filaments lack π-stacking of aromatic side chains and show a conductivity that is 20,000-fold lower than that of OmcZ nanowires. In contrast with surface-displayed type 4 pili, PilA-N-C filaments show structure, function and localization akin to those of type 2 secretion pseudopili6. The secretion of OmcS and OmcZ nanowires is lost when pilA-N is deleted and restored when PilA-N-C filaments are reconstituted. The substitution of pilA-N with the type 4 pili of other microorganisms also causes a loss of secretion of OmcZ nanowires. As all major phyla of prokaryotes use systems similar to type 4 pili, this nanowire translocation machinery may have a widespread effect in identifying the evolution and prevalence of diverse electron-transferring microorganisms and in determining nanowire assembly architecture for designing synthetic protein nanowires.

Investigating aneuploidy-inducing effect of Nemacur, Rogor, and Dursban in human peripheral blood lymphocyte cultures.

For many years, organophosphate (OP) pesticides have been considered an attractive choice for pest control around the world. Excessive use of OPs is a concerning issue for human health. Although the genotoxic effect of these pesticides has been reported, studies that examined their aneuploidy-inducing effect are limited or absent. Therefore, we sought to investigate the potential of OP pesticides, which are extensively used in the Gaza Strip, to induce aneuploidy in human peripheral blood lymphocyte (PBL) cultures. To achieve this goal, we first assessed the cytotoxic effect of selected concentrations of Nemacur (fenamiphos), Rogor (dimethoate), and Dursban (chlorpyrifos) on human PBL cultures by the MTT assay. Then, fluorescence in situ hybridization (FISH) technique was used to determine the frequency of induced aneuploidy (chromosome loss or gain) in human PBL cultures treated with different concentrations of the three types of OPs. We found that all the OPs treatments used did not show appreciable cytotoxic effects. Increase in frequencies of aneuploidy, chromosome loss, and chromosome gain were observed after each treatment as compared to the results of their respective solvent control cultures, and that increase of aneuploidy was significantly evident at 0.050 mg/ml of Nemacur. It was also noticed that chromosome loss is more frequent than chromosome gain for each concentration of the three types of OPs. While the aneuploidy induction effect of the investigated OPs is not significant (except for the 0.050 mg/ml of Nemacur), these pesticides should be examined further since many people are exposed to them.

Microencapsulation of benzalkonium chloride enhanced its antibacterial and antibiofilm activities against Listeria monocytogenes and Escherichia coli.

AIMS: In this study, benzalkonium chloride (BAC) microcapsules were developed for surface disinfection purpose and were evaluated against Listeria monocytogenes and Escherichia coli biofilms. METHODS AND RESULTS: Microcapsules were prepared with two different strategies: uncomplexed BAC-microcapsules (UBM) containing BAC and maltodextrins, and complexed BAC-microcapsules (CBM) containing BAC complexed by pectin and maltodextrins. The minimum inhibitory concentrations (MICs) of free and microencapsulated BAC were investigated against two food pathogens: L. monocytogenes and E. coli. The antibiofilm activities of UBM and CBM against L. monocytogenes and E. coli biofilms formed on stainless steel at 37°C were evaluated and compared to BAC used under its free form. MICs of encapsulated BAC were up to fourfold lower than those of free BAC. The UBM and CBM showed higher antibiofilm effect when compared to the free BAC. CONCLUSIONS: Overall, results demonstrated that microencapsulation enhanced the antibacterial activity of BAC against L. monocytogenes and E. coli biofilms. SIGNIFICANCE AND IMPACT OF THE STUDY: The application of such BAC microcapsule-based delivery systems can improve surface disinfection procedures and reduce the required BAC concentrations and the related cytotoxicity of this antimicrobial compound.

Could Omega 3 fatty acids reduce the risk of contrast-induced nephropathy in patients undergoing coronary angiography? A randomized controlled trial.

Contrast medium-induced nephropathy (CIN) is a leading cause of acquired acute kidney injury and has been associated with prolonged hospitalization and adverse clinical outcomes. This study aimed to determine if omega 3 fatty acids reduce the risk of CIN in patients with chronic kidney disease undergoing coronary angiography. A total of 130 consecutive patients undergoing coronary angiography were randomly assigned to one of two groups as follows: 67 patients were assigned to the N-acetylcysteine (NAC; 1200 mg) and 63 patients were assigned to the omega 3 fatty acid (4 g). Both drugs were administered orally twice per day one day before and on the day of contrast administration. Of the 130 patients enrolled in this study, 10 (7.7%) experienced an increase of at least 0.5 mg/dL (44 µmol/L) in serum creatinine levels 48 h after administration of the contrast agent including 5 of the 67 patients in the NAC group (7.5%) and 5 of the 63 patients in the omega 3 fatty acids group (7.9%; P = 0.919). There were no significant differences in the need for renal replacement therapy (3.0% vs. 9.5%, P = 0.121) or in the mortality rate (3.0% vs. 6.3%, P = 0.361) between the two groups. Short-term prophylactic omega 3 fatty acid treatment with hydration does not reduce the risk of CIN in patients with chronic kidney disease undergoing coronary angiography.

Categorized Genetic Analysis in Childhood-Onset Cardiomyopathy.

BACKGROUND: Childhood-onset cardiomyopathy is a heterogeneous group of conditions the cause of which is largely unknown. The influence of consanguinity on the genetics of cardiomyopathy has not been addressed at a large scale. METHODS: To unravel the genetic cause of childhood-onset cardiomyopathy in a consanguineous population, a categorized approach was adopted. Cases with childhood-onset cardiomyopathy were consecutively recruited. Based on the likelihood of founder mutation and on the clinical diagnosis, genetic test was categorized to either (1) targeted genetic test with targeted mutation test, single-gene test, or multigene panel for Noonan syndrome, or (2) untargeted genetic test with whole-exome sequencing or whole-genome sequencing. Several bioinformatics tools were used to filter the variants. RESULTS: Two-hundred five unrelated probands with various forms of cardiomyopathy were evaluated. The median age of presentation was 10 months. In 30.2% (n=62), targeted genetic test had a yield of 82.7% compared with 33.6% for whole-exome sequencing/whole-genome sequencing (n=143) giving an overall yield of 53.7%. Strikingly, 96.4% of the variants were homozygous, 9% of which were found in 4 dominant genes. Homozygous variants were also detected in 7 novel candidates (ACACB, AASDH, CASZ1, FLII, RHBDF1, RPL3L, ULK1). CONCLUSIONS: Our work demonstrates the impact of consanguinity on the genetics of childhood-onset cardiomyopathy, the value of adopting a categorized population-sensitive genetic approach, and the opportunity of uncovering novel genes. Our data suggest that if a founder mutation is not suspected, adopting whole-exome sequencing/whole-genome sequencing as a first-line test should be considered.

Partial Trisomy of Chromosome 13 with a Novel Translocation (8 ; 13) and Unique Clinical Presentation in a Palestinian Infant.

Partial trisomy 13 is a rare syndrome that usually culminates in death within the first six months of the infant's life. We present a rare case of partial trisomy 13q with exclusive clinical manifestations. The full-term male baby was born by normal vaginal delivery, his birth weight was 3500 grams, and head circumference was 30 cm. He had dysmorphic features in the form of microcephaly, trigonocephaly, depressed nose bridge, hypotelorism, long philtrum, high arch palate, left-sided inguinal hernia, hydrocele, and laryngomalacia. He was operated for pyloric stenosis at the age of 28 days. He also had left-sided severe pelvic-ureteral junction stenosis which was repaired by nephrostomy followed by pyeloplasty. Furthermore, he had right-sided vesicoureteral reflux grade III, right-sided hydronephrosis, small ventricular septum defect, small atrial septum defect, left lung lower lobe sequestration, and craniosynostosis of metopic suture. The baby had global developmental delay and failure to thrive. Cytogenetic study showed a 46,XY, der(8)t(8;13)(p23;q14) karyotype, emphasizing a partial trisomy 13q syndrome with a concomitant partial monosomy in 8p. The baby passed away, in the intensive care unit, at the age of 7 months due to respiratory failure resulting from recurrent chest infections. This is the first reported case of a partial trisomy 13q associated with chromosome 8 with unique clinical presentations. Cytogenetic study for both parents is recommended in order to pinpoint the origin of the translocation and to provide the proper counseling for the family.

Peritoneal dialysis related infections in a tertiary care hospital in Riyadh, Saudi Arabia.

OBJECTIVES: To detect the incidence of and risk factors for infections among patients with end-stage renal disease (ESRD) undergoing peritoneal dialysis (PD). METHODS: A retrospective cohort study was conducted at the PD unit of King Fahad Medical City. End-stage renal disease patients above the age of 12 years who were undergoing PD management between January 2006 and March 2016 were included. RESULTS: One hundred PD patients were enrolled in the study and examined over a total observation period of 2,553 patient-months. The leading ESRD etiology was hypertension (26.3%). The mean duration of PD was 28.05 months. A total of 45 patients developed 101 episodes of technique-related infections (TRIs). Peritonitis represented the majority of these episodes (90 episodes), with an overall rate of one episode per 28.3 patient-months. TRIs were mostly caused by coagulase-negative staphylococci. A total of 12 patients developed non-technique related infections (NTRIs). There was a statistically significant difference between patients with TRI and non-infected patients regarding the presence of diabetes and duration of dialysis. No peritonitis-related deaths were noted. In total, 21 patients continued on PD and 18 patients were shifted to hemodialysis (HD). Conclusion: In our setting, ESRD patients undergoing PD are more susceptible to TRIs than NTRIs. Diabetes increases the risk of developing TRIs. The high incidence of coagulase-negative staphylococcal TRI suggests touch contamination.

Suscepibility of Anopheles gambiae sl and Culex quinquefasciatus to diverse insecticides in the city of N'Djamena.

Mosquito resistance to insecticides remains a major concern for vector control programs based on chemical methods. Hence, a thorough knowledge of vector susceptibility to products recommended for public health is required for effective vector control programs. In this study, we assessed the susceptibility of wild Anopheles gambiae sl and Culex quinquefasciatus populations from N'Djamena (Chad) to four insecticide classes recommended for public health. The study took place from July to October 2014. Following WHO guidelines, bioassays were performed on two- to four-day-old, non-engorged female mosquitoes of both species, collected in the field. The insecticides used were deltamethrin (0.05%), permethrin (1%), DDT (4%), bendiocarb (0.01%), and malathion (5%). Anopheles gambiae sl showed full susceptibility to bendiocarb and malathion but was resistant to pyrethroids; mortality rates were 2% for deltamethrin, 2% for permethrin, and 0% for DDT. Culex quinquefasciatus was susceptible to malathion but resistant to the other insecticides, with a mortality rate of 22% for deltamethrin, 29% for permethrin, 23% for DDT, and 45% bendiocarb. The resistance of Anopheles gambiae sl and of Culex quinquefasciatus may affect the population's adherence to the use of insecticide-treated mosquito nets. Malaria control programs are advised to extend insecticide resistance monitoring to the main culicide species that bite human populations.

Cast accuracy obtained from different impression techniques at different implant angulations (in vitro study).

BACKGROUND: Angulated implants may result in inaccurate impressions, and the impression technique may affect the accuracy of the definitive cast. This study was designed to compare the dimensional accuracy of casts obtained from three impression techniques for three definitive lower casts with implants at different angulations. METHODS: Three Osseolink implants were placed in three reference models with different angles (parallel, 15° and 30°). Impressions of each model were made with three techniques (n = 10 per group): indirect, unsplinted direct, and acrylic resin-splinted direct technique. Impressions were poured with type IV dental stone. Inter-implant distances were measured for casts using a coordinate measuring machine, and the deviations from the reference models (Δr) were calculated. Data were analyzed using one-way ANOVA followed by post hoc tests to detect significance between groups (α = 0.05). RESULTS: This study showed that the deviations in micrometers from the reference model were the least for acrylic resin-splinted direct technique (Δr1 = 49.96, Δr2 = 50.36) versus indirect (Δr1 = 93.8, Δr2 = 90.9) and unsplinted direct techniques ((Δr1 = 67.07, Δr2 = 68.66) in 30° angulated implant situation (p value < 0.0001* for both Δr1 and Δr2). In 15° angulated implants, both the acrylic resin-splinted direct (Δr1 = 44.64, Δr2 = 45.58) and unsplinted direct techniques (Δr1 = 47.39, Δr2 = 55.28) were more accurate than indirect technique (Δr1 = 64.8, Δr2 = 68.3) (p value < 0.0001* for both Δr1 and Δr2). While in parallel condition, no difference was found between all three techniques (p value = 0.085, 0.056 for Δr1 and Δr2, respectively). CONCLUSIONS: The impression technique affected the accuracy of definitive casts. The acrylic resin splinted direct technique produced the most accurate casts, followed by direct unsplinted and indirect techniques. Furthermore, implant angulation affected the impression accuracy. When implant angulation increased from parallel implants to 30°, the forces of deformation increased, which resulted in increased distortion.

The FlaG regulator is involved in length control of the polar flagella of Campylobacter jejuni.

Campylobacter jejuni cells have bipolar flagella. Both flagella have similar lengths of about one helical turn, or 3.53±0.52 µm. The flagellar filament is composed of two homologous flagellins: FlaA and FlaB. Mutant strains that express either FlaA or FlaB alone produce filaments that are shorter than those of the wild-type. It is reported that the flaG gene could affect filament length in some species of bacteria, but its function remains unknown. We introduced a flaG-deletion mutation into the C. jejuni wild-type strain and flaA- or flaB-deletion mutant strains, and observed their flagella by microscopy. The ΔflaG mutant cells produced long filaments of two helical turns in the wild-type background. The ΔflaAG double mutant cells produced very short FlaB filaments. On the other hand, ΔflaBG double mutant cells produced long FlaA filaments and their morphology was not helical but straight. Furthermore, FlaG was secreted, and a pulldown assay showed that sigma factor 28 was co-precipitated with purified polyhistidine-tagged FlaG. We conclude that FlaG controls flagella length by negatively regulating FlaA filament assembly and discuss the role of FlaA and FlaB flagellins in C. jejuni flagella formation.

Structural destabilization of tropomyosin induced by the cardiomyopathy-linked mutation R21H.

The missense mutation R21H in striated muscle tropomyosin is associated with hypertrophic cardiomyopathy, a genetic cardiac disease and a leading cause of sudden cardiac death in young people. Tropomyosin adopts conformation of a coiled coil which is critical for regulation of muscle contraction. In this study, we investigated the effects of the R21H mutation on the coiled-coil structure of tropomyosin and its interactions with its binding partners, tropomodulin and leiomodin. Using circular dichroism and isothermal titration calorimetry, we found that the mutation profoundly destabilized the structural integrity of αTM1a1-28 Zip, a chimeric peptide containing the first 28 residues of tropomyosin. The mutated αTM1a1-28 Zip was still able to interact with tropomodulin and leiomodin. However, the mutation resulted in a ∼30-fold decrease of αTM1a1-28 Zip's binding affinity to leiomodin. We used a crystal structure of αTM1a1-28 Zip that we solved at 1.5 Å resolution to study the mutation's effect in silico by means of molecular dynamics simulation. The simulation data indicated that while the mutation disrupted αTM1a1-28 Zip's coiled-coil structure, most notably from residue Ala18 to residue His31, it may not affect the N-terminal end of tropomyosin. The drastic decrease of αTM1a1-28 Zip's affinity to leiomodin caused by the mutation may lead to changes in the dynamics at the pointed end of thin filaments. Therefore, the R21H mutation is likely interfering with the regulation of the normal thin filament length essential for proper muscle contraction.

Structure of FlgK reveals the divergence of the bacterial Hook-Filament Junction of Campylobacter.

Evolution of a nano-machine consisting of multiple parts, each with a specific function, is a complex process. A change in one part should eventually result in changes in other parts, if the overall function is to be conserved. In bacterial flagella, the filament and the hook have distinct functions and their respective proteins, FliC and FlgE, have different three-dimensional structures. The filament functions as a helical propeller and the hook as a flexible universal joint. Two proteins, FlgK and FlgL, assure a smooth connectivity between the hook and the filament. Here we show that, in Campylobacter, the 3D structure of FlgK differs from that of its orthologs in Salmonella and Burkholderia, whose structures have previously been solved. Docking the model of the FlgK junction onto the structure of the Campylobacter hook provides some clues about its divergence. These data suggest how evolutionary pressure to adapt to structural constraints, due to the structure of Campylobacter hook, causes divergence of one element of a supra-molecular complex in order to maintain the function of the entire flagellar assembly.