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Fulltext BRCA2 Hypomorphic Missense Variants Confer Moderate Risks of Breast Cancer

Shimelis H, Mesman RLS, Von Nicolai C, Ehlen A, Guidugli L, Martin C, et al.

Cancer Res, 2017 Jun 01;77(11):2789-2799.
PMID: 28283652 DOI: 10.1158/0008-5472.CAN-16-2568

Breast cancer risks conferred by many germline missense variants in the BRCA1 and BRCA2 genes, often referred to as variants of uncertain significance (VUS), have not been established. In this study, associations between 19 BRCA1 and 33 BRCA2 missense substitution variants and breast cancer risk were investigated through a breast cancer case-control study using genotyping data from 38 studies of predominantly European ancestry (41,890 cases and 41,607 controls) and nine studies of Asian ancestry (6,269 cases and 6,624 controls). The BRCA2 c.9104A>C, p.Tyr3035Ser (OR = 2.52; P = 0.04), and BRCA1 c.5096G>A, p.Arg1699Gln (OR = 4.29; P = 0.009) variant were associated with moderately increased risks of breast cancer among Europeans, whereas BRCA2 c.7522G>A, p.Gly2508Ser (OR = 2.68; P = 0.004), and c.8187G>T, p.Lys2729Asn (OR = 1.4; P = 0.004) were associated with moderate and low risks of breast cancer among Asians. Functional characterization of the BRCA2 variants using four quantitative assays showed reduced BRCA2 activity for p.Tyr3035Ser compared with wild-type. Overall, our results show how BRCA2 missense variants that influence protein function can confer clinically relevant, moderately increased risks of breast cancer, with potential implications for risk management guidelines in women with these specific variants. Cancer Res; 77(11); 2789-99. ©2017 AACR.

Matched MeSH terms: Amino Acid Substitution
Fulltext Changes in the amino acid sequence of the recombinant human factor VIIa analog, vatreptacog alfa, are associated with clinical immunogenicity

Mahlangu JN, Weldingh KN, Lentz SR, Kaicker S, Karim FA, Matsushita T, et al.

J Thromb Haemost, 2015 Nov;13(11):1989-98.
PMID: 26362483 DOI: 10.1111/jth.13141

BACKGROUND: Vatreptacog alfa, a recombinant human factor VIIa (rFVIIa) analog developed to improve the treatment of bleeds in hemophilia patients with inhibitors, differs from native FVIIa by three amino acid substitutions. In a randomized, double-blind, crossover, confirmatory phase III trial (adept(™) 2), 8/72 (11%) hemophilia A or B patients with inhibitors treated for acute bleeds developed anti-drug antibodies (ADAs) to vatreptacog alfa.
OBJECTIVES: To characterize the formation of anti-vatreptacog alfa ADAs in hemophilia patients with inhibitors.
METHODS/PATIENTS: This was a post hoc analysis of adept(™) 2. Immunoglobulin isotype determination, specificity analysis of rFVIIa cross-reactive antibodies, epitope mapping of rFVIIa single mutant analogs and pharmacokinetic (PK) profiling were performed to characterize the ADAs.
RESULTS: Immunoglobulin isotyping indicated that the ADAs were of the immunoglobulin G subtype. In epitope mapping, none of the rFVIIa single mutant analogs (V158D, E296V or M298Q) contained the complete antibody epitope, confirming that the antibodies were specific for vatreptacog alfa. In two patients, for whom PK profiling was performed both before and after the development of ADAs, vatreptacog alfa showed a prolonged elimination phase following ADA development. During the follow-up evaluation, the rFVIIa cross-reactivity disappeared after the last vatreptacog alfa exposure, despite continued exposure to rFVIIa as part of standard care.
CONCLUSIONS: Results from the vatreptacog alfa phase III trial demonstrate that the specific changes made, albeit relatively small, to the FVIIa molecule alter its clinical immunogenicity.

Matched MeSH terms: Amino Acid Substitution*
Fulltext Analysis of sequence variations in low-density lipoprotein receptor gene among Malaysian patients with familial hypercholesterolemia

Al-Khateeb A, Zahri MK, Mohamed MS, Sasongko TH, Ibrahim S, Yusof Z, et al.

BMC Med Genet, 2011;12:40.
PMID: 21418584 DOI: 10.1186/1471-2350-12-40

Familial hypercholesterolemia is a genetic disorder mainly caused by defects in the low-density lipoprotein receptor gene. Few and limited analyses of familial hypercholesterolemia have been performed in Malaysia, and the underlying mutations therefore remain largely unknown.We studied a group of 154 unrelated FH patients from a northern area of Malaysia (Kelantan). The promoter region and exons 2-15 of the LDLR gene were screened by denaturing high-performance liquid chromatography to detect short deletions and nucleotide substitutions, and by multiplex ligation-dependent probe amplification to detect large rearrangements.

Matched MeSH terms: Amino Acid Substitution
Structural and kinetic studies of a novel nerol dehydrogenase from Persicaria minor, a nerol-specific enzyme for citral biosynthesis

Tan CS, Hassan M, Mohamed Hussein ZA, Ismail I, Ho KL, Ng CL, et al.

Plant Physiol Biochem, 2018 Feb;123:359-368.
PMID: 29304481 DOI: 10.1016/j.plaphy.2017.12.033

Geraniol degradation pathway has long been elucidated in microorganisms through bioconversion studies, yet weakly characterised in plants; enzyme with specific nerol-oxidising activity has not been reported. A novel cDNA encodes nerol dehydrogenase (PmNeDH) was isolated from Persicaria minor. The recombinant PmNeDH (rPmNeDH) is a homodimeric enzyme that belongs to MDR (medium-chain dehydrogenases/reductases) superfamily that catalyses the first oxidative step of geraniol degradation pathway in citral biosynthesis. Kinetic analysis revealed that rPmNeDH has a high specificity for allylic primary alcohols with backbone ≤10 carbons. rPmNeDH has ∼3 fold higher affinity towards nerol (cis-3,7-dimethyl-2,6-octadien-1-ol) than its trans-isomer, geraniol. To our knowledge, this is the first alcohol dehydrogenase with higher preference towards nerol, suggesting that nerol can be effective substrate for citral biosynthesis in P. minor. The rPmNeDH crystal structure (1.54 Å) showed high similarity with enzyme structures from MDR superfamily. Structure guided mutation was conducted to describe the relationships between substrate specificity and residue substitutions in the active site. Kinetics analyses of wild-type rPmNeDH and several active site mutants demonstrated that the substrate specificity of rPmNeDH can be altered by changing any selected active site residues (Asp280, Leu294 and Ala303). Interestingly, the L294F, A303F and A303G mutants were able to revamp the substrate preference towards geraniol. Furthermore, mutant that exhibited a broader substrate range was also obtained. This study demonstrates that P. minor may have evolved to contain enzyme that optimally recognise cis-configured nerol as substrate. rPmNeDH structure provides new insights into the substrate specificity and active site plasticity in MDR superfamily.

Matched MeSH terms: Amino Acid Substitution
Existence of two forms of L protein of Newcastle disease virus isolates due to a compensatory mutation in Domain V

Kusumaningtyas E, Tan WS, Zamrod Z, Eshaghi M, Yusoff K

Arch Virol, 2004 Sep;149(9):1859-65.
PMID: 15593426

Nucleotide sequence comparison of the L gene of the Malaysian neurotropic-viscerotropic velogenic NDV strain AF2240 with other NDV strains revealed a single nucleotide insertion at position 3870. This mutation is compensated by a nucleotide deletion downstream at position 3958 which results in two forms of the L proteins containing a 30-amino acid substitution in Domain V. This compensatory mutation does not correlate with the pathogenicity of the viral strains but it may affect the viral replication as Domain V is believed to play an important role in the replication of paramyxoviruses.

Matched MeSH terms: Amino Acid Substitution
A nonsense mutation in exon 8 of the APC gene (Arg283Ter) causes clinically variable FAP in a Malaysian Chinese family

Mohamed Z, Ahmad R, Yoke NS, Zakaria Z, Ahmad H, Yew TH

Cancer Sci, 2003 Aug;94(8):725-8.
PMID: 12901799 DOI: 10.1111/j.1349-7006.2003.tb01509.x

The present study was carried out to characterize the causative genetic mutation in a medium-sized Malaysian Chinese pedigree of three generations affected with familial adenomatous polyposis (FAP). Clinical data and genetic studies revealed considerable phenotypic variability in affected individuals in this family. Blood was obtained from members of the FAP-01 family and genomic DNA was extracted. Mutation screening of the adenomatous polyposis coli (APC) gene was carried out using the single strand conformation polymorphism (SSCP) technique. The possibility of exon skipping was predicted by splicing motif recognition software (ESEfinder release2.0). SSCP results showed mobility shifts in exon 8 of the APC gene which segregated with affected members of the family. Sequence analysis revealed that the affected individuals are heterozygous for a C847T transition, whilst all the unaffected family members and control individuals are homozygous C at the same position. This nucleotide substitution generates a stop codon at amino acid position 283, in place of the usual arginine (Arg283Ter). We conclude that an Arg283Ter mutation in the APC gene is causative of the FAP phenotype in this family, although there is considerable variation in the presentation of this disease among affected individuals. Computational analysis predicts that this mutation occurs within sequences that may function as splicing signals, so that the sequence change may affect normal splicing.

Matched MeSH terms: Amino Acid Substitution
Identification of a novel HLA-A*01 variant, HLA-A*01:211, in a Singaporean Malay bone marrow donor

Kaur A, Cho L, Cereb N, Lin PY, Yang KL

HLA, 2020 09;96(3):329-330.
PMID: 32227684 DOI: 10.1111/tan.13884

One nucleotide substitution in codon 73 of HLA-A*01:01:01:01 results in a novel allele, HLA-A*01:211.

Matched MeSH terms: Amino Acid Substitution
HLA-B*15:349:02, a novel variant of HLA-B*15, discovered in a Singaporean Malay bone marrow donor

Cho L, Kaur A, Cereb N, Lin PY, Yang KL

HLA, 2020 09;96(3):344-345.
PMID: 32212215 DOI: 10.1111/tan.13879

One nucleotide substitution in codon 112 of HLA-B*15:349:01 results in a novel allele, HLA-B*15:349:02.

Matched MeSH terms: Amino Acid Substitution
Fulltext Monoclonal antibody-escape variant of dengue virus serotype 1: Genetic composition and envelope protein expression

Chem YK, Chua KB, Malik Y, Voon K

Trop Biomed, 2015 Jun;32(2):344-51.
PMID: 26691263 MyJurnal

Monoclonal antibody-escape variant of dengue virus type 1 (MabEV DEN-1) was discovered and isolated in an outbreak of dengue in Klang Valley, Malaysia from December 2004 to March 2005. This study was done to investigate whether DEN152 (an isolate of MabEV DEN-1) is a product of recombination event or not. In addition, the non-synonymous mutations that correlate with the monoclonal antibody-escape variant were determined in this study. The genomes of DEN152 and two new DEN-1 isolates, DENB04 and DENK154 were completely sequenced, aligned, and compared. Phylogenetic tree was plotted and the recombination event on DEN152 was investigated. DEN152 is sub-grouped under genotype I and is closely related genetically to a DEN-1 isolated in Japan in 2004. DEN152 is not a recombinant product of any parental strains. Four amino acid substitutions were unique only to DEN 152. These amino acid substitutions were (Ser)[326](Leu), (Ser)[340](Leu) at the deduced E protein, (Ile)[250](Thr) at NS1 protein, and (Thr)[41](Ser) at NS5 protein. Thus, DEN152 is an isolate of the emerging monoclonal antibody-escape variant DEN-1 that escaped diagnostic laboratory detection.

Matched MeSH terms: Amino Acid Substitution
Fulltext Characterization of BRCA1 and BRCA2 variants in multi-ethnic Asian cohort from a Malaysian case-control study

Lai KN, Ho WK, Kang IN, Kang PC, Phuah SY, Mariapun S, et al.

BMC Cancer, 2017 02 22;17(1):149.
PMID: 28222693 DOI: 10.1186/s12885-017-3099-6

BACKGROUND: Genetic testing for BRCA1 and BRCA2 has led to the accurate identification of individuals at higher risk of cancer and the development of new therapies. Approximately 10-20% of the genetic testing for BRCA1 and BRCA2 leads to the identification of variants of uncertain significance (VUS), with higher proportions in Asians. We investigated the functional significance of 7 BRCA1 and 25 BRCA2 variants in a multi-ethnic Asian cohort using a case-control approach.
METHODS: The MassARRAY genotyping was conducted in 1,394 Chinese, 406 Malay and 310 Indian breast cancer cases and 1,071 Chinese, 167 Malay and 255 Indian healthy controls. The association of individual variant with breast cancer risk was analyzed using logistic regression model adjusted for ethnicity, age and family history.
RESULTS: Our study confirmed BRCA2 p.Ile3412Val is presented in >2% of unaffected women and is likely benign, and BRCA2 p.Ala1996Thr which is predicted to be likely pathogenic by in-silico models is presented in 2% of healthy Indian women suggesting that it may not be associated with breast cancer risk. Single-variant analysis suggests that BRCA1 p.Arg762Ser may be associated with breast cancer risk (OR = 7.4; 95% CI, 0.9-62.3; p = 0.06).
CONCLUSIONS: Our study shows that BRCA2 p.Ile3412Val and p.Ala1996Thr are likely benign and highlights the need for population-specific studies to determine the likely functional significance of population-specific variants. Our study also suggests that BRCA1 p.Arg762Ser may be associated with increased risk of breast cancer but other methods or larger studies are required to determine a more precise estimate of breast cancer risk.

Matched MeSH terms: Amino Acid Substitution
Fulltext Epidemiological and Evolutionary Dynamics of Influenza B Viruses in Malaysia, 2012-2014

Oong XY, Ng KT, Lam TT, Pang YK, Chan KG, Hanafi NS, et al.

PLoS One, 2015;10(8):e0136254.
PMID: 26313754 DOI: 10.1371/journal.pone.0136254

Epidemiological and evolutionary dynamics of influenza B Victoria and Yamagata lineages remained poorly understood in the tropical Southeast Asia region, despite causing seasonal outbreaks worldwide. From 2012-2014, nasopharyngeal swab samples collected from outpatients experiencing acute upper respiratory tract infection symptoms in Kuala Lumpur, Malaysia, were screened for influenza viruses using a multiplex RT-PCR assay. Among 2,010/3,935 (51.1%) patients infected with at least one respiratory virus, 287 (14.3%) and 183 (9.1%) samples were tested positive for influenza A and B viruses, respectively. Influenza-positive cases correlate significantly with meteorological factors-total amount of rainfall, relative humidity, number of rain days, ground temperature and particulate matter (PM10). Phylogenetic reconstruction of haemagglutinin (HA) gene from 168 influenza B viruses grouped them into Yamagata Clade 3 (65, 38.7%), Yamagata Clade 2 (48, 28.6%) and Victoria Clade 1 (55, 32.7%). With neuraminidase (NA) phylogeny, 30 intra-clade (29 within Yamagata Clade 3, 1 within Victoria Clade 1) and 1 inter-clade (Yamagata Clade 2-HA/Yamagata Clade 3-NA) reassortants were identified. Study of virus temporal dynamics revealed a lineage shift from Victoria to Yamagata (2012-2013), and a clade shift from Yamagata Clade 2 to Clade 3 (2013-2014). Yamagata Clade 3 predominating in 2014 consisted of intra-clade reassortants that were closely related to a recent WHO vaccine candidate strain (B/Phuket/3073/2013), with the reassortment event occurred approximately 2 years ago based on Bayesian molecular clock estimation. Malaysian Victoria Clade 1 viruses carried H274Y substitution in the active site of neuraminidase, which confers resistance to oseltamivir. Statistical analyses on clinical and demographic data showed Yamagata-infected patients were older and more likely to experience headache while Victoria-infected patients were more likely to experience nasal congestion and sore throat. This study describes the evolution of influenza B viruses in Malaysia and highlights the importance of continuous surveillance for better vaccination policy in this region.

Matched MeSH terms: Amino Acid Substitution
Fulltext Mutations in the tail domain of MYH3 contributes to atrial septal defect

Maran S, Ee R, Faten SA, Sy Bing C, Khaw KY, Erin Lim SH, et al.

PLoS One, 2020;15(4):e0230982.
PMID: 32315303 DOI: 10.1371/journal.pone.0230982

Atrial septal defect (ASD) is one of the most common congenital heart defects diagnosed in children. Sarcomeric genes has been attributed to ASD and knockdown of MYH3 functionally homologues gene in chick models indicated abnormal atrial septal development. Here, we report for the first time, a case-control study investigating the role of MYH3 among non-syndromic ASD patients in contributing to septal development. Four amplicons which will amplifies the 40 kb MYH3 were designed and amplified using long range-PCR. The amplicons were then sequenced using indexed paired-end libraries on the MiSeq platform. The STREGA guidelines were applied for planning and reporting. The non-synonymous c. 3574G>A (p.Ala1192Thr) [p = 0.001, OR = 2.30 (1.36-3.87)] located within the tail domain indicated a highly conserved protein region. The mutant model of c. 3574G>A (p.Ala1192Thr) showed high root mean square deviation (RMSD) values compared to the wild model. To our knowledge, this is the first study to provide compelling evidence on the pathogenesis of MYH3 variants towards ASD hence, suggesting the crucial role of non-synonymous variants in the tail domain of MYH3 towards atrial septal development. It is hoped that this gene can be used as panel for diagnosis of ASD in future.

Matched MeSH terms: Amino Acid Substitution
A molecular dynamics approach to explore the structural characterization of cataract causing mutation R58H on human γD crystallin

Karunakaran R, Srikumar PS

Mol Cell Biochem, 2018 Dec;449(1-2):55-62.
PMID: 29532225 DOI: 10.1007/s11010-018-3342-8

The crystallins are a family of monomeric proteins present in the mammalian lens and mutations in these proteins cause various forms of cataracts. The aim of our current study is to emphasize the structural characterization of aggregation propensity of mutation R58H on γD crystallin using molecular dynamics (MD) approach. MD result revealed that difference in the sequence level display a wide variation in the backbone atomic position, and thus exhibits rigid conformational dynamics. Changes in the flexibility of residues favoured to increase the number of intra-molecular hydrogen bonds in mutant R58H. Moreover, notable changes in the hydrogen bonding interaction resulted to cause the misfolding of mutant R58H by introducing α-helix. Principal component analysis (PCA) result suggested that mutant R58H showed unusual conformational dynamics along the two principal components when compared to the wild-type (WT)-γD crystallin. In a nutshell, the increased surface hydrophobicity could be the cause of self-aggregation of mutant R58H leading to aculeiform cataract.

Matched MeSH terms: Amino Acid Substitution
Fulltext Naturally occurring hepatitis B virus surface antigen mutant variants in Malaysian blood donors and vaccinees

Hudu SA, Harmal NS, Saeed MI, Alshrari AS, Malik YA, Niazlin MT, et al.

Eur J Clin Microbiol Infect Dis, 2015 Jul;34(7):1349-59.
PMID: 25792010 DOI: 10.1007/s10096-015-2358-1

Hepatitis B virus surface mutants are of enormous importance because they are capable of escaping detection by serology and can infect both vaccinated and unvaccinated populations, thus putting the whole population at risk. This study aimed to detect and characterise hepatitis B-escaped mutants among blood donors and vaccinees. One thousand serum samples were collected for this study from blood donors and vaccinees. Hepatitis B surface antigen, antibodies and core antibodies were tested using a commercial enzyme-linked immunosorbent assay (ELISA) kit. DNA detection was performed via nested polymerase chain reaction (PCR), and the S gene was sequenced and analysed using bioinformatics. Of the 1,000 samples that were screened, 5.5% (55/1,000) were found to be HBsAg-negative and anti-HBc- and HBV DNA-positive. All 55 isolates were found to belong to genotype B. Several mutations were found across all the sequences from synonymous and non-synonymous mutations, with the most nucleotide mutations occurring at position 342, where adenine was replaced by guanine, and cytosine at position 46 was replaced by adenine in 96.4% and 98% of the isolates, respectively. Mutation at position 16 of the amino acid sequence was found to be common to all the Malaysian isolates, with 85.7% of the mutations occurring outside the major hydrophilic region. This study revealed a prevalence of 5.5% for hepatitis B-escaped mutations among blood donors and vaccinated undergraduates, with the most common mutation being found at position 16, where glutamine was substituted with lysine.

Matched MeSH terms: Amino Acid Substitution
An Overview of Hepatitis B Virus Surface Antigen Mutant in the Asia Pacific

Hudu SA, Malik YA, Niazlin MT, Harmal NS, Sekawi Z

Curr Issues Mol Biol, 2014;16:69-78.
PMID: 24014801

Hepatitis B virus infection is a serious health problem worldwide, and more than 350 million people are chronic carriers, constituting a major global threat. Southeast Asia and the Western Pacific have the highest levels of endemicity in the world, with an estimated seroprevalence ranging between 2% and 31%. Mutations in the hepatitis B surface antigen (HBsAg) have been reported in many parts of the world but are most common in Asian infants; such mutants have several clinical effects, such as the development of hepatocellular carcinoma. Diagnostic failures by commercial assays have reduced the diagnostic effectiveness of HBsAg detection. For example the substitution of an amino acid in the major hydrophilic region of the S gene reduces the binding of hepatitis B surface antibodies leading to immune escape. The safety of blood transfusion may be compromised by current screening tests due to escape from being neutralised by antibodies induced by HBsAg mutants, and undetectable levels of viral surface protein. Data on the epidemiology of HBsAg mutation in Asia Pacific are scant; however, this manuscript has reviewed the available information on the epidemiology of HBsAg mutation in Asia Pacific.

Matched MeSH terms: Amino Acid Substitution
Molecular characterization of genes encoding the quinolone resistance determining regions of Malaysian Streptococcus pneumoniae strains

Kumari N, Subramaniam G, Navaratnam P, Sekaran SD

Indian J Med Microbiol, 2008 5 1;26(2):148-50.
PMID: 18445951

Genes encoding the quinolones resistance determining regions (QRDRs) in Streptococcus pneumoniae were detected by PCR and the sequence analysis was carried out to identify point mutations within these regions. The study was carried out to observe mutation patterns among S. pneumoniae strains in Malaysia. Antimicrobial susceptibility testing of 100 isolates was determined against various antibiotics, out of which 56 strains were categorised to have reduced susceptibility to ciprofloxacin (>or=2 microg/mL). These strains were subjected to PCR amplification for presence of the gyrA, parC , gyrB and parE genes. Eight representative strains with various susceptibilities to fluoroquinolones were sequenced. Two out of the eight isolates that were sequenced were shown to have a point mutation in the gyrA gene at position Ser81. The detection of mutation at codon Ser81 of the gyrA gene suggested the potential of developing fluoroquinolone resistance among S. pneumoniae isolates in Malaysia. However, further experimental work is required to confirm the involvement of this mutation in the development of fluoroquinolone resistance in Malaysia.

Matched MeSH terms: Amino Acid Substitution/genetics
Mutations in gyrA and parC in ciprofloxacin-resistant Neisseria gonorrhoeae in Kuala Lumpur, Malaysia

Karunakaran R, Sam IC

J Antimicrob Chemother, 2007 Apr;59(4):803-4.
PMID: 17329273
Matched MeSH terms: Amino Acid Substitution
High level expression of thermostable lipase from Geobacillus sp. strain T1

Leow TC, Rahman RN, Basri M, Salleh AB

Biosci Biotechnol Biochem, 2004 Jan;68(1):96-103.
PMID: 14745170

A thermostable extracellular lipase of Geobacillus sp. strain T1 was cloned in a prokaryotic system. Sequence analysis revealed an open reading frame of 1,251 bp in length which codes for a polypeptide of 416 amino acid residues. The polypeptide was composed of a signal peptide (28 amino acids) and a mature protein of 388 amino acids. Instead of Gly, Ala was substituted as the first residue of the conserved pentapeptide Gly-X-Ser-X-Gly. Successful gene expression was obtained with pBAD, pRSET, pET, and pGEX as under the control of araBAD, T7, T7 lac, and tac promoters, respectively. Among them, pGEX had a specific activity of 30.19 Umg(-1) which corresponds to 2927.15 Ug(-1) of wet cells after optimization. The recombinant lipase had an optimum temperature and pH of 65 degrees C and pH 9, respectively. It was stable up to 65 degrees C at pH 7 and active over a wide pH range (pH 6-11). This study presents a rapid cloning and overexpression, aimed at improving the enzyme yield for successful industrial application.

Matched MeSH terms: Amino Acid Substitution
The Effects of One Amino Acid Substitutions at the C-Terminal Region of Thermostable L2 Lipase by Computational and Experimental Approach

Sani HA, Shariff FM, Rahman RNZRA, Leow TC, Salleh AB

Mol Biotechnol, 2018 Jan;60(1):1-11.
PMID: 29058211 DOI: 10.1007/s12033-017-0038-3

The substitutions of the amino acid at the predetermined critical point at the C-terminal of L2 lipase may increase its thermostability and enzymatic activity, or even otherwise speed up the unfolding of the protein structure. The C-terminal of most proteins is often flexible and disordered. However, some protein functions are directly related to flexibility and play significant role in enzyme reaction. The critical point for mutation of L2 lipase structure was predicted at the position 385 of the L2 sequence, and the best three mutants were determined based on I-Mutant2.0 software. The best three mutants were S385E, S385I and S385V. The effects of the substitution of the amino acids at the critical point were analysed with molecular dynamics simulation by using Yet Another Scientific Artificial Reality Application software. The predicted mutant L2 lipases were found to have lower root mean square deviation value as compared to L2 lipase. It was indicated that all the three mutants had higher compactness in the structure, consequently enhanced the stability. Root mean square fluctuation analysis showed that the flexibility of L2 lipase was reduced by mutations. Purified S385E lipase had an optimum temperature of 80 °C in Tris-HCl pH 8. The highest enzymatic activity of purified S385E lipase was obtained at 80 °C temperature in Tris-HCl pH 8, while for L2 lipase it was at 70 °C in Glycine-NaOH pH 9. The thermal stability of S385V lipase was enhanced as compared to other protein since that the melting point (T m) value was at 85.96 °C. S385I lipase was more thermostable compared to recombinant L2 lipase and other mutants at temperature 60 °C within 16 h preincubation.

Matched MeSH terms: Amino Acid Substitution
Fulltext Monitoring of the h275y mutation in pandemic influenza A(H1N1) 2009 strains isolated in Malaysia

Suppiah J, Yusof MA, Othman KA, Saraswathy TS, Thayan R, Kasim FM, et al.

Southeast Asian J. Trop. Med. Public Health, 2011 Jan;42(1):100-4.
PMID: 21323171

The 2009 pandemic influenza A(H1N1) infection in Malaysia was first reported in May 2009 and oseltamivir was advocated for confirmed cases in postexposure prophylaxis. However, there are cases of oseltamivir-resistance reported among H1N1-positive patients in other countries. Resistance is due to substitution of histidine by tyrosine at residue 275 (H275Y) of neuraminidase (NA). In this study, we have employed Sanger sequencing method to investigate the occurrence of mutations in NA segments of 67 pandemic 2009 A(H1N1) viral isolates from Malaysian patients that could lead to probable oseltamivir resistance. The sequencing analysis did not yield mutation at residue 275 for all 67 isolates indicating that our viral isolates belong to the wild type and do not confer resistance to oseltamivir.

Matched MeSH terms: Amino Acid Substitution

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