Molecular Epidemiology and Mechanisms of 43 Low-Level Linezolid-Resistant Enterococcus faecalis Strains in Chongqing, China

BACKGROUND: Enterococcus faecalis strains with low-level resistance to linezolid (an oxazolidinone antibiotic) have become common. No large-scale study has examined the underlying mechanisms in linezolid-resistant E. faecalis (LRE) strains. We investigated these mechanisms and molecular characteristics in Chongqing, China. METHODS: A total of 1,120 non-duplicated E. faecalis strains collected from August 2014 to June 2017 underwent drug susceptibility testing. LRE strains were screened for optrA, cfr, and mutations in the 23S rRNA and ribosomal proteins L3 and L4 by PCR amplification and sequencing. Multi-locus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE) were used for epidemiological analysis. RESULTS: All 43 low-level LRE strains (minimum inhibitory concentration: 8–16 mg/L) harbored optrA; cfr and 23S rRNA mutations were not detected. Novel mutations in the ribosomal proteins L3 and L4—one deletion (Q103del) and four substitutions (S113L, T35A, I98V, and N79D)—were identified. Novel amino acid substitutions at positions E60K, G197D, and T285P of the OptrA protein were observed. MLST revealed 20 types of LRE strains; the most common type was ST16 (32.6%). PFGE showed 14 strains of ST16 with unique banding patterns. Eight novel sequence types (ST823 to ST830) and one allele (gki95) were identified for the first time in China. CONCLUSIONS: optrA plays an important role in linezolid resistance and may serve as a marker for resistance screening. Since the L3 and L4 mutations did not simultaneously occur in the same strain, they play a negligible role in linezolid resistance. Epidemiological investigation suggested that the LRE cases were sporadic.

First Case in Korea of Group B Streptococcus With Reduced Penicillin Susceptibility Harboring Amino Acid Substitutions in Penicillin-Binding Protein 2X

No abstract available.

Whole exome sequencing and pedigree analysis for a case with an ABw03 subtype / 中华医学遗传学杂志

OBJECTIVE@#To explore the molecular basis for a blood donor with an ABO subtype.@*METHODS@#The proband and his family members were subjected to serological analysis. Their genotypes were determined by real-time PCR and sequencing of the coding regions of ABO gene.@*RESULTS@#The proband was determined as an ABw subtype. By sequencing analysis, the proband was typed as A102/BW03. Compared with ABO*B.01, the proband was found to harbor a 721C>T variant (ABO*BW.03 allele) in exon 7 of the ABO gene, which caused substitution of Arginine at position 241 by Tryptophan resulting in a ABW phenotype. The blood type of the proband's sister was similar to that of the proband. The maternal serological pattern was B type, and the result of sequencing suggested that the genotype fit with B101/Bw03.@*CONCLUSION@#The 721C>T in the exon 7 of the ABO glycosyltransferase gene probably underlies the Bw03 phenotype. The ABO*Bw.03 variant of the proband and his sister were inherited from their mother.

Antimicrobial resistance profiles of vancomycin-resistant Enterococcus species isolated from laboratory mice

Isolates of 24 enterococci, 5 Enterococcus casseliflavus and 19 Enterococcus gallinarum, possessing vanC genes and showing low-level resistance to vancomycin were obtained from mice from commercial mouse breeding companies. Since some of these isolates showed resistance to other antibiotics, the purpose of this study was to clarify the resistant profiles of these isolates. One E. casseliflavus isolate showed resistance to erythromycin with a minimal inhibitory concentration (MIC) of 8 μg/mL and also showed apparent resistance to fluoroquinolones with an MIC of 32 μg/mL for ciprofloxacin. The MICs of 2 other fluoroquinolone-resistant E. casseliflavus and E. gallinarum isolates were 3 and 6 μg/mL, respectively. These 3 resistant isolates showed an absence of macrolide- and fluoroquinolone-resistant genes, including amino acid substitutions in the quinolone resistance determining regions of DNA gyrase and topoisomerase IV. Resistance to tetracycline was detected in 2 E. gallinarum isolates that were highly resistant, exhibiting MICs of 48 and 64 μg/mL and possessing tet(O) genes. The results indicate that antibiotic-resistant enterococci are being maintained in some laboratory mouse strains that have never been treated with an antibiotic.

Evolution of equine influenza viruses (H3N8) during a Brazilian outbreak, 2015

Abstract Equine influenza is one of the major respiratory infectious diseases in horses. An equine influenza virus outbreak was identified in vaccinated and unvaccinated horses in a veterinary school hospital in São Paulo, SP, Brazil, in September 2015. The twelve equine influenza viruses isolated belonged to Florida Clade 1. The hemagglutinin and neuraminidase amino acid sequences were compared with the recent isolates from North and South America and the World Organisation for Animal Health recommended Florida Clade 1 vaccine strain. The hemagglutinin amino acid sequences had nine substitutions, compared with the vaccine strain. Two of them were in antigenic site A (A138S and G142R), one in antigenic site E (R62K) and another not in antigenic site (K304E). The four substitutions changed the hydrophobicity of hemagglutinin. Three distinct genetic variants were identified during the outbreak. Eleven variants were found in four quasispecies, which suggests the equine influenza virus evolved during the outbreak. The use of an out of date vaccine strain or updated vaccines without the production of protective antibody titers might be the major contributing factors on virus dissemination during this outbreak.

Structure analysis of capsid protein of Porcine circovirus type 2 from pigs with systemic disease

Abstract Economic losses with high mortality rate associated with Porcine circovirus type 2 (PCV2) is reported worldwide. PCV2 commercial vaccine was introduced in 2006 in U.S. and in 2008 in Brazil. Although PCV2 vaccines have been widely used, cases of PCV2 systemic disease have been reported in the last years. Eleven nursery or fattening pigs suffering from PCV2 systemic disease were selected from eight PCV2-vaccinated farms with historical records of PCV2 systemic disease in Southern Brazil. PCV2 genomes were amplified and sequenced from lymph node samples of selected pigs. The comparison among the ORF2 amino acid sequences of PCV2 isolates revealed three amino acid substitutions in the positions F57I, N178S and A190T, respectively. Using molecular modeling, a structural model for the capsid protein of PCV2 was built. Afterwards, the mutated residues positions were identified in the model. The structural analysis of the mutated residues showed that the external residue 190 is close to an important predicted region for antibodies recognition. Therefore, changes in the viral protein conformation might lead to an inefficient antibody binding and this could be a relevant mechanism underlying the recent vaccine failures observed in swine farms in Brazil.

Identification of a novel Ax allele of the ABO blood group / 中华医学遗传学杂志

OBJECTIVE@#To explore the molecular basis for an individual with Ax28 phenotype of the ABO subtype.@*METHODS@#The ABO group antigens on red blood cells of the proband were identified by monoclonal antibodies. The ABO antibody in serum was detected by standard A, B, O cells. Exons 1 to 7 of the ABO gene were respectively amplified by PCR and directly sequenced. Amplicons for exons 5 to 7 were also sequenced after cloning.@*RESULTS@#Weakened A antigen was detected on red blood cells from the proband. Both anti-A and anti-B antibodies were detected in the serum. Heterozygous 261G/del was detected in exon 6, while heterozygous 467C/T and 830T/C were detected in exon 7 by direct DNA sequencing. After cloning and sequencing, two alleles (O01 and Ax28) were obtained. Compared with A102, the sequence of Ax28 contained one nucleotide changes (T to C) at position 830, which resulted in amino acid change (Val to Ala) at position 277.@*CONCLUSION@#The novel mutation c.830T>C of the galactosaminyltransferase gene may give rise to the Ax28 phenotype.

Molecular basis of the B(A) phenotype / 中华医学遗传学杂志

OBJECTIVE@#To explore the serological and molecular characteristics of a female with the B(A) phenotype and safety issues related to her blood transfusion.@*METHODS@#The B(A) phenotype of the proband was confirmed by serological testing. Her genotype was determined by using polymerase chain reaction-sequence specific primer (PCR-SSP) and direct sequencing of exons 6 and 7 of the ABO locus. Clinical condition of her blood transfusion was also reviewed.@*RESULTS@#Both A and B antigens were detected on the red blood cells derived from the proband, while anti-A antibody was detected in her serum. The result of PCR-SSP suggested that she has a B/O02 phenotype. DNA sequencing revealed presence of 297A>G, 526C>G, 657C>T, 700C>G, 703G>A, 796C>A, 803G>C and 930G>A mutations. The genotype of the proband was deduced as B(A) 02/O02. Compared with the B101 allele, the B(A)02 allele has a nucleotide change (C>G) at position 700, which resulted in substitution of an amino acid (P234A). The result of cross match testing between the proband and two donors with an AB phenotype was consistent. No adverse reaction was observed after the transfusion.@*CONCLUSION@#700G>C of B allele can result in the B(A) phenotype, which is similar to AB. Blood donors for individuals with the B(A) phenotype should include those with an AB phenotype.

Prevalência de hemoglobinas variantes em comunidades quilombolas no estado do Piauí, Brasil / Prevalence of hemoglobin variants in quilombola communities in the state of Piauí, Brazil

Resumo As hemoglobinas variantes (Hb) decorrem de mutações nos genes da globina. As variantes estruturais mais frequentes são HbS, HbC, HbD e HbE. O gene da hemoglobina S tem frequência elevada na América, enquanto que no Brasil é maior no Sudeste e Nordeste. O presente artigo tem por objetivo investigar a presença de hemoglobinas variantes em 15 comunidades quilombolas do estado do Piauí. Foram analisadas 1.239 amostras, nas quais as hemoglobinas foram triadas pela cromatografia líquida de alta eficiência (HPLC). Aplicou-se questionário referente a gênero, etnia e consanguinidade das populações. Das 1.239 amostras, 5,4% apresentaram o traço falciforme AS, as doenças falciformes SS e SC apareceram em 0,8% do total, nas hemoglobinas AC, AD e DD. Das 1.069 pessoas negras, 84 apresentaram alteração das hemoglobinas; destas, 34 eram do sexo masculino e 53 do feminino. Ocorreu a presença de 13 casamentos consanguíneos dentre as 84 alterações das hemoglobinas. O estudo das hemoglobinas variantes em 15 comunidades remanescentes de quilombos do Piauí contribui para sua educação em saúde frente aos aspectos da herança genética destas proteínas, relevante questão de saúde pública, proporcionando subsídios para a implantação do Programa Estadual da Doença Falciforme do Piauí.

Abstract Hemoglobin variants (Hb) result from mutations in globin genes, with amino acid substitution in the polypeptide chain. Among the most common structural variants are HbS, HbC, HbD and HbE. The S hemoglobin gene is a high frequency gene across America and Brazil, where it is more frequent in the Southeast and Northeast. The scope of this article is to investigate the presence of hemoglobin variants in 15 quilombos (fugitive slave communities) of Piaui. The sample was of 1,239 people and hemoglobin was screened by high-performance liquid chromatography (HPLC). A questionnaire was applied related to gender, ethnicity and consanguinity. Of the samples analyzed, 5.4% had AS sickle cell trait, while SS and SC sickle cell anemia showed a rate of 0.8%, with AC, AD and DD hemoglobin. Of the 1,069 Afro-descendants, 84 revealed hemoglobin abnormalities, 34 being male 53 being female. There were 13 consanguineous marriages among the 84 hemoglobin alterations. The study of hemoglobin variants in 15 former quilombo communities in the state of Piaui contributes to their education in health in the aspects of genetic inheritance of hemoglobin, a relevant public health issue, providing input for the implementation of the State Program of Sickle Cell Disease of Piaui.

A case of Bw39 subtype caused by 562C to T mutation of exon 7 of α -1,3-D-galactosyltransferase gene / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To analyze a sample with ABO subgroup using serological and molecular methods.</p><p><b>METHODS</b>The ABO phenotype of the sample was determined with a tube method, and the activity of glycosyltransferases was determined with an uridine diphosphate galactose transferring method. The ABO gene of the propositus was identified by PCR with sequence-specific primers (PCR-SSP). In addition, exons 6 and 7 of the ABO gene were cloned and sequenced.</p><p><b>RESULTS</b>Neither A nor B antigen was identified in the propositus, despite that its anti-B antibody was found to be attenuated. No activity of α -1, 3-D-galactosyltransferase was detected in the serum. The presence of B and O alleles were confirmed by PCR-SSP, and a novel mutation (562C to T) of the exon 7 was confirmed by sequencing, which has led to an amino acid substitution (Arg to Cys) at position 188. The genotype of the propositus was determined as Bnew/O.</p><p><b>CONCLUSION</b>A novel B allele has been identified, which was named as Bw39 by the Blood Group Antigen Gene Mutation Database (BGMUT).</p>

Clinically Significant Unclassified Variants in BRCA1 and BRCA2 genes among Korean Breast Cancer Patients / Journal of the Korean Cancer Association, 대한암학회지

PURPOSE: Unclassified variants (UVs) of BRCA1 and BRCA2 genes are not defined as pathogenic for breast cancer, and their clinical significance currently remains undefined. Therefore, this study was conducted to identify potentially pathogenic UVs by comparing their prevalence between breast cancer patients and controls. MATERIALS AND METHODS: A total of 328 breast cancer patients underwent BRCA1/2 genetic screening at the National Cancer Center of Korea. Genetic variants of BRCA genes that were categorized as unclassified according to the Breast Cancer Information Core database were selected based on allelic frequency, after which candidate variants were genotyped in 421 healthy controls. We also examined family members of the study participants. Finally, the effects of amino acid substitutions on protein structure and function were predicted in silico. RESULTS: Genetic tests revealed 33 UVs in BRCA1 and 47 in BRCA2. Among 15 candidates genotyped in healthy controls, c.5339T>C in BRCA1 and c.6029T>G, c.7522G>A in BRCA2 were not detected. Moreover, the c.5339T>C variant in the BRCA1 gene was detected in four patients with a family history of breast cancer. This nonsynonymous variant (Leu1780Pro) in the BRCA1 C-terminal domain was predicted to have an effect on BRCA1 protein structure/function. CONCLUSION: This study showed that comparison of genotype frequency between cases and controls could help identify UVs of BRCA genes that are potentially pathogenic. Moreover, ourfindings suggest that c.5339T>C in BRCA1 might be a pathogenic variant for patients and their families.

Conservation of matrix protein genes in rabies viruses circulating in South Korea since 1999

Rabies virus (RABV) causes a neurological disease in warm-blooded animals that is nearly always fatal. In this study, we analyzed the matrix (M) genes in 10 Korean street RABV strains isolated from two Provinces during 2011–2013. The M genes in these 10 Korean strains were highly conserved during 1999–2013. Phylogenetic analysis revealed they were closely related to the M genes of RABVs isolated in northeastern China. Specific amino acid substitutions were identified in the KRVB1206, KRVF1301, and BV9901PJ strains. However, functional domains, including those involved in virus production and pathogenicity, were conserved in all 10 strains.

Diverse Phenotypic Expression of Cardiomyopathies in a Family with TNNI3 p.Arg145Trp Mutation

Genetic diagnosis of cardiomyopathies is challenging, due to the marked genetic and allelic heterogeneity and the lack of knowledge of the mutations that lead to clinical phenotypes. Here, we present the case of a large family, in which a single TNNI3 mutation caused variable phenotypic expression, ranging from restrictive cardiomyopathy (RCMP) to hypertrophic cardiomyopathy (HCMP) to near-normal phenotype. The proband was a 57-year-old female with HCMP. Examining the family history revealed that her elder sister had expired due to severe RCMP. Using a next-generation sequencing-based gene panel to analyze the proband, we identified a known TNNI3 gene mutation, c.433C>T, which is predicted to cause an amino acid substitution (p.Arg145Trp) in the highly conserved inhibitory region of the cardiac troponin I protein. Sanger sequencing confirmed that six relatives with RCMP or near-normal phenotypes also carried this mutation. To our knowledge, this is the first genetically confirmed family with diverse phenotypic expression of cardiomyopathies in Korea. Our findings demonstrate familial implications, where a single mutation in a sarcomere protein can cause diverse phenotypic expression of cardiomyopathies.

Clinical Manifestations and Treatment in Korean Patients with X-Linked Agammaglobulinemia

PURPOSE: X-linked agammaglobulinemia (XLA) is a primary immunodeficiency caused by mutations in the Bruton's tyrosine kinase (Btk) gene. The aim of this study was to investigate the clinical manifestations, molecular features, and treatment status of XLA in Korean patients at Seoul National University Children's Hospital. METHODS: Fourteen Korean boys with XLA showing serum agammaglobulinemia, non-detectable to less than 2% of peripheral B-cells, and mutation of the Btk gene were enrolled. We observed the clinical features, laboratory findings, status of treatment, and complications in these XLA patients. RESULTS: All XLA patients had a history of recurrent bacterial infections before diagnosis, and 20% of them had a neutropenia. Of the XLA patients 35.7% had a family history of XLA and 75% of their mothers were carriers. Btk gene analysis showed variable gene mutations in Xq22 including 9 amino acid substitutions, 3 frameshifts, 1 premature stop codon, and 1 splice defect. After intravenous immunoglobulin replacement therapy, infection episodes decreased, but complications such as bronchiectasis and chronic sinusitis remained. CONCLUSIONS: In patients less than 4 years of age with recurrent infection, analysis of serum gamma globulin levels and the Btk gene are recommended for the early diagnosis of XLA and for the appropriate prevention of recurrent infection.

Clinical Manifestations and Treatment in Korean Patients with X-Linked Agammaglobulinemia

PURPOSE: X-linked agammaglobulinemia (XLA) is a primary immunodeficiency caused by mutations in the Bruton's tyrosine kinase (Btk) gene. The aim of this study was to investigate the clinical manifestations, molecular features, and treatment status of XLA in Korean patients at Seoul National University Children's Hospital. METHODS: Fourteen Korean boys with XLA showing serum agammaglobulinemia, non-detectable to less than 2% of peripheral B-cells, and mutation of the Btk gene were enrolled. We observed the clinical features, laboratory findings, status of treatment, and complications in these XLA patients. RESULTS: All XLA patients had a history of recurrent bacterial infections before diagnosis, and 20% of them had a neutropenia. Of the XLA patients 35.7% had a family history of XLA and 75% of their mothers were carriers. Btk gene analysis showed variable gene mutations in Xq22 including 9 amino acid substitutions, 3 frameshifts, 1 premature stop codon, and 1 splice defect. After intravenous immunoglobulin replacement therapy, infection episodes decreased, but complications such as bronchiectasis and chronic sinusitis remained. CONCLUSIONS: In patients less than 4 years of age with recurrent infection, analysis of serum gamma globulin levels and the Btk gene are recommended for the early diagnosis of XLA and for the appropriate prevention of recurrent infection.

Genetic Variations of the KISS1R Gene in Korean Girls with Central Precocious Puberty

The timing of puberty onset varies greatly among individuals, and much of this variation is modulated by genetic factors. This study aimed to identify the kisspeptin receptor (KISS1R) gene variations and to investigate the associations between these variations and central precocious puberty (CPP). Korean girls with CPP (n = 194) and their healthy controls (n = 99) were included in this study. The entire coding region and the exon-intron boundaries (exon 1 through 5) of the KISS1R gene were directly sequenced. Seven polymorphisms were identified in the KISS1R gene. A missense change c.1091T>A, and an intron variant c.738+64G>T showed significantly higher allele frequencies in CPP patients than in controls (c.1091T>A: 30.7% vs. 22.2%, P = 0.031; c.738+64G>T: 45.6% vs. 35.9%, P = 0.023). The missense variant (c.1091T>A) was a nonsynonymous polymorphism that induces amino acid substitution of p.Leu364His. The haplotype CAGTGTC was detected more frequently in the CPP group (P = 0.042). The sequence variants of the KISS1R gene can be inducible factors in the development of CPP. The association between sequence variants and CPP should be validated by further evidence obtained from larger samples of children with CPP.

Phylogenetic analysis of Dengue virus 1 isolated from South Minas Gerais, Brazil

Abstract Dengue is a major worldwide public health problem, especially in the tropical and subtropical regions of the world. Primary infection with a single Dengue virus serotype causes a mild, self-limiting febrile illness called dengue fever. However, a subset of patients who experience secondary infection with a different serotype can progress to a more severe form of the disease, called dengue hemorrhagic fever. The four Dengue virus serotypes (1–4) are antigenically and genetically distinct and each serotype is composed of multiple genotypes. In this study we isolated one Dengue virus 1 serotype, named BR/Alfenas/2012, from a patient with dengue hemorrhagic fever in Alfenas, South Minas Gerais, Brazil and molecular identification was performed based on the analysis of NS5 gene. Swiss mice were infected with this isolate to verify its potential to induce histopathological alterations characteristic of dengue. Liver histopathological analysis of infected animals showed the presence of inflammatory infiltrates, hepatic steatosis, as well as edema, hemorrhage and necrosis focal points. Phylogenetic and evolutionary analyses based on the envelope gene provided evidence that the isolate BR/Alfenas/2012 belongs to genotype V, lineage I and it is probably derived from isolates of Rio de Janeiro, Brazil. The isolate BR/Alfenas/2012 showed two unique amino acids substitutions (SER222THRE and PHE306SER) when compared to other Brazilian isolates from the same genotype/lineage. Molecular models were generated for the envelope protein indicating that the amino acid alteration PHE 306 SER could contribute to a different folding in this region located within the domain III. Further genetic and animal model studies using BR/Alfenas/2012 and other isolates belonging to the same lineage/genotype could help determine the relation of these genetic alterations and dengue hemorrhagic fever in a susceptible population.

Effect of Amino Acid Polymorphisms of House Dust Mite Der p 2 Variants on Allergic Sensitization

PURPOSE: The sequence variations of the Der p 2 allergen of Dermatophagoides pteronyssinus diverge along 2 pathways with particular amino acid substitutions at positions 40,47,111, and 114. The environmental prevalence and IgE binding to Der p 2 variants differ among regions. To compare IgE binding to Der p 2 variants between sera from Bangkok, Thailand and Perth, Western Australia with different variants and to determine the variant-specificity of antibodies induced by vaccination with recombinant variants. METHODS: The structures of recombinant variants produced in yeast were compared by circular dichroism and 1-anilinonaphthalene 8-sulfonic acid staining of their lipid-binding cavity. Sera from subjects in Bangkok and Perth where different variants are found were compared by the affinity (IC50) of IgE cross-reactivity to different variants and by direct IgE binding. Mice were immunized with the variants Der p 2.0101 and Der p 2.0110, and their IgG binding to Der p 2.0103, 2.0104, and 2.0109 was measured. RESULTS: The secondary structures of the recombinant variants resembled the natural allergen but with differences in ANS binding. The IC50 of Der p 2.0101 required 7-fold higher concentrations to inhibit IgE binding to the high-IgE-binding Der p 2.0104 than for homologous inhibition in sera from Bangkok where it is absent, while in sera from Perth that have both variants the IC50 was the same and low. Reciprocal results were obtained for Der p 2.0110 not found in Perth. Direct binding revealed that Der p 2.0104 was best for detecting IgE in both regions, followed by Der p 2.0101 with binding to other variants showing larger differences. Mouse anti-Der p 2.0101 antibodies had a high affinity of cross-reactivity but bound poorly to other variants. CONCLUSIONS: The affinity of IgE antibody cross-reactivity, the direct IgE binding, and the specificities of antibodies induced by vaccination show that measures of allergic sensitization and therapeutic strategies could be optimized with knowledge of Der p 2 variants.

Site-specific PEGylation of recombinant lysostaphin / 生物工程学报

Lysostaphin (Lysn) is an antibacterial metalloendopeptidase that cleaves the pentaglycin bridges in the cell wall of Staphylococci. Although many studies have demonstrated its high activity in vitro, the medical application of Lysn has been hampered by its short half-life in vivo. In order to enhance its stability in vivo without significantly suppressing the enzymatic activity, we designed and tested eight single cysteine substitutions in Lysn for covalent attachment of polyethylene glycol chains (PEGylation). The purified mutants, fully reduced by Dithiothreitol (DTT), were treated with mPEG-MAL(20 kDa). The PEG modification efficiency was above 70% as determined by reverse-phase high-pressure liquid chromatography (HPLC) analysis. The PEG-Lysn proteins were further purified by cation exchange chromatography (MacroCap SP), reaching at least 95% purity. The activities of the PEG-Lysn proteins were determined by the turbidity and minimum inhibitory concentration (MIC) assays. We found that the PEGylated V240C and T244C mutants retained about 50% of the original antibacterial activity of Lysn. Overall, this study will help develop highly stable and active PEG-Lysn to treat systemic S. aureus infections.

Cataract-causing mutation S228P promotes βB1-crystallin aggregation and degradation by separating two interacting loops in C-terminal domain

β/γ-Crystallins are predominant structural proteins in the cytoplasm of lens fiber cells and share a similar fold composing of four Greek-key motifs divided into two domains. Numerous cataract-causing mutations have been identified in various β/γ-crystallins, but the mechanisms underlying cataract caused by most mutations remains uncharacterized. The S228P mutation in βB1-crystallin has been linked to autosomal dominant congenital nuclear cataract. Here we found that the S228P mutant was prone to aggregate and degrade in both of the human and E. coli cells. The intracellular S228P aggregates could be redissolved by lanosterol. The S228P mutation modified the refolding pathway of βB1-crystallin by affecting the formation of the dimeric intermediate but not the monomeric intermediate. Compared with native βB1-crystallin, the refolded S228P protein had less packed structures, unquenched Trp fluorophores and increased hydrophobic exposure. The refolded S228P protein was prone to aggregate at the physiological temperature and decreased the protective effect of βB1-crystallin on βA3-crystallin. Molecular dynamic simulation studies indicated that the mutation decreased the subunit binding energy and modified the distribution of surface electrostatic potentials. More importantly, the mutation separated two interacting loops in the C-terminal domain, which shielded the hydrophobic core from solvent in native βB1-crystallin. These two interacting loops are highly conserved in both of the N- and C-terminal domains of all β/γ-crystallins. We propose that these two interacting loops play an important role in the folding and structural stability of β/γ-crystallin domains by protecting the hydrophobic core from solvent access.