title: Helicobacter pylori single-stranded DNA binding protein--functional characterization and modulation of H. pylori DnaB helicase activity.
abstract: Helicobacter pylori, an important bacterial pathogen, causes gastric ulcer and gastric adenocarcinoma in humans. The fundamentals of basic biology such as DNA replication are poorly understood in this pathogen. In the present study, we report the cloning and functional characterization of the single-stranded DNA (ssDNA) binding protein from H. pylori. The N-terminal DNA binding domain shows significant homology with E. coli single-stranded DNA binding protein (SSB), whereas the C-terminal domain shows less homology. The overall DNA-binding activity and tetramerization properties, however, remain unaffected. In in vitro experiments with purified proteins, H. pylori (Hp) SSB bound specifically to ssDNA and modulated the enzymatic ATPase and helicase activity of HpDnaB helicase. HpSSB and HpDnaB proteins were co-localized in sharp, distinct foci in exponentially growing H. pylori cells, whereas both were spread over large areas in its dormant coccoid form, suggesting the absence of active replication forks in the latter. These results confirm the multiple roles of SSB during DNA replication and provide evidence for altered replicative metabolism in the spiral and coccoid forms that may be central to the bacterial physiology and pathogenesis.
authors.affiliation: Special Centre for Molecular Medicine, Jawaharlal Nehru University, New Delhi, India.
authors.forename: Atul
authors.initials: A
authors.lastname: Sharma
authors.forename: Ram G
authors.initials: RG
authors.lastname: Nitharwal
authors.forename: Bhupender
authors.initials: B
authors.lastname: Singh
authors.forename: Ashraf
authors.initials: A
authors.lastname: Dar
authors.forename: Santanu
authors.initials: S
authors.lastname: Dasgupta
authors.forename: Suman K
authors.initials: SK
authors.lastname: Dhar
mesh_terms: D000595:Amino Acid Sequence; D003001:Cloning, Molecular; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D053488:DnaB Helicases / Q000378:metabolism*; D004926:Escherichia coli / Q000737:chemistry / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000378:metabolism; D015870:Gene Expression; D016480:Helicobacter pylori / Q000737:chemistry / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D050296:Microbial Viability; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
chemical_list: D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D053488:DnaB Helicases