title: Structure of the gene 2.5 protein, a single-stranded DNA binding protein encoded by bacteriophage T7.
abstract: The gene 2.5 protein (gp2.5) of bacteriophage T7 is a single-stranded DNA (ssDNA) binding protein that has essential roles in DNA replication and recombination. In addition to binding DNA, gp2.5 physically interacts with T7 DNA polymerase and T7 primase-helicase during replication to coordinate events at the replication fork. We have determined a 1.9-A crystal structure of gp2.5 and show that it has a conserved OB-fold (oligosaccharide/oligonucleotide binding fold) that is well adapted for interactions with ssDNA. Superposition of the OB-folds of gp2.5 and other ssDNA binding proteins reveals a conserved patch of aromatic residues that stack against the bases of ssDNA in the other crystal structures, suggesting that gp2.5 binds to ssDNA in a similar manner. An acidic C-terminal extension of the gp2.5 protein, which is required for dimer formation and for interactions with the T7 DNA polymerase and the primase-helicase, appears to be flexible and may act as a switch that modulates the DNA binding affinity of gp2.5.
authors.affiliation: Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA.
authors.forename: T
authors.initials: T
authors.lastname: Hollis
authors.forename: J M
authors.initials: JM
authors.lastname: Stattel
authors.forename: D S
authors.initials: DS
authors.lastname: Walther
authors.forename: C C
authors.initials: CC
authors.lastname: Richardson
authors.forename: T
authors.initials: T
authors.lastname: Ellenberger
mesh_terms: D000595:Amino Acid Sequence; D017123:Bacteriophage T7 / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D018360:Crystallography, X-Ray; D004277:DNA, Single-Stranded / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000235:genetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014764:Viral Proteins / Q000737:chemistry* / Q000235:genetics
chemical_list: D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins; D014764:Viral Proteins; C085913:gene 2.5 protein, Enterobacteria phage T7