title: Complexed crystal structure of replication restart primosome protein PriB reveals a novel single-stranded DNA-binding mode.
abstract: PriB is a primosomal protein required for replication restart in Escherichia coli. PriB stimulates PriA helicase activity via interaction with single-stranded DNA (ssDNA), but the molecular details of this interaction remain unclear. Here, we report the crystal structure of PriB complexed with a 15 bases oligonucleotide (dT15) at 2.7 A resolution. PriB shares structural similarity with the E.coli ssDNA-binding protein (EcoSSB). However, the structure of the PriB-dT15 complex reveals that PriB binds ssDNA differently. Results from filter-binding assays show that PriB-ssDNA interaction is salt-sensitive and cooperative. Mutational analysis suggests that the loop L45 plays an important role in ssDNA binding. Based on the crystal structure and biochemical analyses, we propose a cooperative mechanism for the binding of PriB to ssDNA and a model for the assembly of the PriA-PriB-ssDNA complex. This report presents the first structure of a replication restart primosomal protein complexed with DNA, and a novel model that explains the interactions between a dimeric oligonucleotide-binding-fold protein and ssDNA.
authors.affiliation: Institute of Molecular Biology, Academia Sinica, Taipei, 115, Taiwan.
authors.forename: Cheng-Yang
authors.initials: CY
authors.lastname: Huang
authors.forename: Che-Hsiung
authors.initials: CH
authors.lastname: Hsu
authors.forename: Yuh-Ju
authors.initials: YJ
authors.lastname: Sun
authors.forename: Huey-Nan
authors.initials: HN
authors.lastname: Wu
authors.forename: Chwan-Deng
authors.initials: CD
authors.lastname: Hsiao
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D018360:Crystallography, X-Ray; D004270:DNA, Circular / Q000737:chemistry / Q000378:metabolism; D004277:DNA, Single-Stranded / Q000737:chemistry* / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D019281:Dimerization; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D009841:Oligonucleotides / Q000737:chemistry; D011485:Protein Binding; D016415:Sequence Alignment
chemical_list: D004270:DNA, Circular; D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D009841:Oligonucleotides; C086004:PriB protein, E coli; C476430:SSB protein, E coli