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169 results on '"Sau, Subrata"'

14. Promoter analysis of the cap8 operon, involved in type 8 capsular polysaccharide production in Staphylococcus aureus

Author

Ouyang, Shu, Sau, Subrata, and Lee, Chia Y.

Subjects
Staphylococcus aureus -- Genetic aspects, Operons -- Research, Microbial polysaccharides -- Research, Protein binding -- Research, Binding sites (Biochemistry) -- Research, Gene expression -- Research, Genetic regulation -- Research, Biological sciences
Abstract

The production of type 8 capsular polysaccharide (CP8) in Staphylococcus aureus was investigated using deletion analysis and site-directed mutagenesis. Several inverted and direct repeats were found upstream of the cap8 promoter gene. Results also revealed that a cis-acting element was required for cap8 activity and CP8 production and serves as a positive regulatory protein binding site.

Published
1999

16. The Staphylococcus aureus allelic genetic loci for serotype 5 and 8 capsule expression contain the type-specific genes flanked by common genes

Author

Sau, Subrata, Bhasin, Navneet, Wann, Elisabeth R., Lee, Jean C., Foster, Timothy J., and Lee, Chia Y.

Subjects
Staphylococcus aureus -- Research, Nucleotide sequence -- Analysis, Polysaccharides -- Genetic aspects, Biological sciences
Abstract

The mapping of the cap5(8) locus on the Staphylococcus aureaus chromosome and the nucleotide sequences of the cap5 and cap8 gene clusters were reported. It was found that the DNA sequences which contain 12 of the 16 open reading frames of the cap5 and cap8 gene clusters are almost identical. The possible functions of these open reading in CP5 and CP8 biosynthesis were also discussed.

Published
1997

17. Molecular characterization and transcriptional analysis of tye 8 capsule genes in Staphylococcus aureus

Author

Sau, Subrata, Sun, Jiwen, and Lee, Chia Y.

Subjects
Bacterial genetics -- Research, Staphylococcus aureus -- Genetic aspects, Nucleotide sequence -- Analysis, Biological sciences
Abstract

The cap8 capsule gene cluster of Staphylococcus aureus was analyzed by via genetic complementation tests, promoter cloning and Northern blot analysis to characterize its gene structure. The Staphylococcus aureus type eight capsule gene cluster is composed of 16 open reading frames such as cap8H, cap8I, cap8J and cap8K which were involved in the synthesis of type eight capsular polysaccharides (CP8). Gene-specific mutagenesis of the eleven open reading frames of the cap8 gene cluster altered CP8 biosynthesis in Staphylococcus aureus.

Published
1997

18. Cloning of type 8 capsule genes and analysis of gene clusters for the production of different capsular polysaccharides in Staphylococcus aureus

Author

Sau, Subrata and Lee, Chia Y.

Subjects
Staphylococcus aureus -- Genetic aspects, Polysaccharides -- Research, Biological sciences
Abstract

Type 8 capsule (cap8) genes from Staphylococcus aureus were cloned and one recombinant plasmid with a 14-kb insert was discovered to complement 14 of the 18 type 8 capsule-negative (Cap8-) mutants employed in the study. The cap genes were found to be clustered. DNA fragments containing the cap8 gene cluster indicated extensive homology with all 17 strains tested, including type 1 strains. Strain M had an additional capsule gene cluster which was unlike the cap1 gene cluster.

Published
1996

23. Repressor of temperate mycobacteriophage L1 harbors a stable C-terminal domain and binds to different asymmetric operator DNAs with variable affinity

Author

Mandal Nitai C, Das Malabika, Chanda Palas K, Chattoraj Partho, Bandhu Amitava, Ganguly Tridib, and Sau Subrata

Subjects
Infectious and parasitic diseases, RC109-216
Abstract

Abstract Background Lysogenic mode of life cycle of a temperate bacteriophage is generally maintained by a protein called 'repressor'. Repressor proteins of temperate lambdoid phages bind to a few symmetric operator DNAs in order to regulate their gene expression. In contrast, repressor molecules of temperate mycobacteriophages and some other phages bind to multiple asymmetric operator DNAs. Very little is known at present about the structure-function relationship of any mycobacteriophage repressor. Results Using highly purified repressor (CI) of temperate mycobacteriophage L1, we have demonstrated here that L1 CI harbors an N-terminal domain (NTD) and a C-terminal domain (CTD) which are separated by a small hinge region. Interestingly, CTD is more compact than NTD at 25°C. Both CTD and CI contain significant amount of α-helix at 30°C but unfold partly at 42°C. At nearly 200 nM concentration, both proteins form appreciable amount of dimers in solution. Additional studies reveal that CI binds to O64 and OL types of asymmetric operators of L1 with variable affinity at 25°C. Interestingly, repressor – operator interaction is affected drastically at 42°C. The conformational change of CI is most possibly responsible for its reduced operator binding affinity at 42°C. Conclusion Repressors encoded by mycobacteriophages differ significantly from the repressor proteins of λ and related phages at functional level but at structural level they are nearly similar.

Published
2007
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26. Regions and residues of an asymmetric operator DNA interacting with the monomeric repressor of temperate mycobacteriophage L1

Author

Bandhu, Amitava, Ganguly, Tridib, Jana, Biswanath, Mondal, Rajkrishna, and Sau, Subrata

Subjects
Bacteriophages -- Physiological aspects, Bacteriophages -- Genetic aspects, DNA -- Structure, DNA -- Chemical properties, Methyl groups -- Chemical properties, Proteins -- Structure, Proteins -- Analysis, Biological sciences, Chemistry
Abstract

Various in vitro experiments were performed to gain insight into the the structure of the repressor protein of mycobacteriophage L1, a repressor-asymmetric operator DNA complex. The tertiary structure of the L1 repressor-operator DNA complex is found to be distinct from those of the lambdoid phages even though the number of repressor molecules per operator site closely matched that of the [lambda] phage system.

Published
2010

27. Alternative Sigma Factor of Staphylococcus aureusInteracts with the Cognate Antisigma Factor Primarily Using Its Domain 3

Author

Sinha, Debabrata, Sinha, Debasmita, Dutta, Anindya, Chakraborty, Tushar, Mondal, Rajkrishna, Seal, Soham, Poddar, Asim, Chatterjee, Subhrangsu, and Sau, Subrata

Abstract

σB, an alternative sigma factor, is usually employed to tackle the general stress response in Staphylococcus aureusand other Gram-positive bacteria. This protein, involved in S. aureus-mediated pathogenesis, is typically blocked by RsbW, an antisigma factor having serine kinase activity. σB, a σ70-like sigma factor, harbors three conserved domains designated σB2, σB3, and σB4. To better understand the interaction between RsbW and σBor its domains, we have studied their recombinant forms, rRsbW, rσB, rσB2, rσB3, and rσB4, using different probes. The results show that none of the rσBdomains, unlike rσB, showed binding to a cognate DNA in the presence of a core RNA polymerase. However, both rσB2and rσB3, like rσB, interacted with rRsbW, and the order of their rRsbW binding affinity looks like rσB> rσB3> rσB2. Furthermore, the reaction between rRsbW and rσBor rσB3was exothermic and occurred spontaneously. rRsbW and rσB3also associate with each other at a stoichiometry of 2:1, and different types of noncovalent bonds might be responsible for their interaction. A structural model of the RsbW-σB3complex that has supported our experimental results indicated the binding of rσB3at the putative dimeric interface of RsbW. A genetic study shows that the tentative dimer-forming region of RsbW is crucial for preserving its rσBbinding ability, serine kinase activity, and dimerization ability. Additionally, a urea-induced equilibrium unfolding study indicated a notable thermodynamic stabilization of σB3in the presence of RsbW. Possible implications of the stabilization data in drug discovery were discussed at length.

Published
2021
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31. Determining the Roles of a Conserved α-Helix in a Global Virulence Regulator from <italic>Staphylococcus aureus</italic>.

Author

Mahapa, Avisek, Mandal, Sukhendu, Sinha, Debabrata, Sau, Subrata, and Sau, Keya

Subjects
STAPHYLOCOCCUS aureus, ALPHA helix structure (Proteins), VIRULENCE of bacteria, DNA-binding proteins, DIMERIZATION
Abstract

SarA, a pleiotropic transcription regulator, is encoded by Staphylococcus aureus, a pathogenic bacterium. The expression of many virulence and non-virulence genes in S. aureus is modulated by this regulator. Structural studies have shown it to be a winged-helix DNA-binding protein carrying two monomers. Each SarA monomer is composed of five α-helices (α1-α5), three β-strands (β1-β3) and multiple loops. The putative DNA binding region of SarA is constituted with α3, α4, β2, and β3, whereas, its dimerization seems to occur using α1, α2, and α5. Interestingly, many SarA-like proteins are dimeric and use three or more helices for their dimerization. To clearly understand the roles of helix α1 in the dimerization, we have constructed and purified a SarA mutant (Δα1) that lacks helix α1. Our in-depth studies with Δα1 indicate that the helix α1 is critical for preserving the structure, DNA binding activity and thermodynamic stability of SarA. However, the helix has little affected its dimerization ability. Possible reasons for such anomaly have been discussed at length. [ABSTRACT FROM AUTHOR]

Published
2018
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