title: Single-stranded DNA-binding protein complex from Helicobacter pylori suggests an ssDNA-binding surface.
abstract: Single-stranded DNA (ssDNA)-binding protein (SSB) plays an important role in DNA replication, recombination, and repair. SSB consists of an N-terminal ssDNA-binding domain with an oligonucleotide/oligosaccharide binding fold and a flexible C-terminal tail involved in protein-protein interactions. SSB from Helicobacter pylori (HpSSB) was isolated, and the ssDNA-binding characteristics of HpSSB were analyzed by fluorescence titration and electrophoretic mobility shift assay. Tryptophan fluorescence quenching was measured as 61%, and the calculated cooperative affinity was 5.4x10(7) M(-1) with an ssDNA-binding length of 25-30 nt. The crystal structure of the C-terminally truncated protein (HpSSBc) in complex with 35-mer ssDNA [HpSSBc-(dT)(35)] was determined at a resolution of 2.3 A. The HpSSBc monomer folds as an oligonucleotide/oligosaccharide binding fold with a Y-shaped conformation. The ssDNA wrapped around the HpSSBc tetramer through a continuous binding path comprising five essential aromatic residues and a positively charged surface formed by numerous basic residues.
authors.affiliation: Institute of Bioinformatics and Structural Biology, National Tsing Hua University, Hsinchu 300, Taiwan, ROC.
authors.forename: Kun-Wei
authors.initials: KW
authors.lastname: Chan
authors.forename: Yi-Juan
authors.initials: YJ
authors.lastname: Lee
authors.forename: Chia-Hung
authors.initials: CH
authors.lastname: Wang
authors.forename: Haimei
authors.initials: H
authors.lastname: Huang
authors.forename: Yuh-Ju
authors.initials: YJ
authors.lastname: Sun
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism*; D018360:Crystallography, X-Ray; D004277:DNA, Single-Stranded / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000378:metabolism*; D024202:Electrophoretic Mobility Shift Assay; D005470:Fluorometry; D016480:Helicobacter pylori / Q000737:chemistry* / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011485:Protein Binding; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment
chemical_list: D001426:Bacterial Proteins; D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins