title: The carboxyl-terminal domain of bacteriophage T7 single-stranded DNA-binding protein modulates DNA binding and interaction with T7 DNA polymerase.
abstract: Gene 2.5 of bacteriophage T7 is an essential gene that encodes a single-stranded DNA-binding protein (gp2.5). Previous studies have demonstrated that the acidic carboxyl terminus of the protein is essential and that it mediates multiple protein-protein interactions. A screen for lethal mutations in gene 2.5 uncovered a variety of essential amino acids, among which was a single amino acid substitution, F232L, at the carboxyl-terminal residue. gp2.5-F232L exhibits a 3-fold increase in binding affinity for single-stranded DNA and a slightly lower affinity for T7 DNA polymerase when compared with wild type gp2.5. gp2.5-F232L stimulates the activity of T7 DNA polymerase and, in contrast to wild-type gp2.5, promotes strand displacement DNA synthesis by T7 DNA polymerase. A carboxyl-terminal truncation of gene 2.5 protein, gp2.5-Delta 26C, binds single-stranded DNA 40-fold more tightly than the wild-type protein and cannot physically interact with T7 DNA polymerase. gp2.5-Delta 26C is inhibitory for DNA synthesis catalyzed by T7 DNA polymerase on single-stranded DNA, and it does not stimulate strand displacement DNA synthesis at high concentration. The biochemical and genetic data support a model in which the carboxyl-terminal tail modulates DNA binding and mediates essential interactions with T7 DNA polymerase.
authors.affiliation: Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115, USA.
authors.forename: Zheng-Guo
authors.initials: ZG
authors.lastname: He
authors.forename: Lisa F
authors.initials: LF
authors.lastname: Rezende
authors.forename: Smaranda
authors.initials: S
authors.lastname: Willcox
authors.forename: Jack D
authors.initials: JD
authors.lastname: Griffith
authors.forename: Charles C
authors.initials: CC
authors.lastname: Richardson
mesh_terms: D017123:Bacteriophage T7 / Q000737:chemistry*; D002850:Chromatography, Gel; D003001:Cloning, Molecular; D004247:DNA / Q000378:metabolism; D004277:DNA, Single-Stranded / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000502:physiology*; D004259:DNA-Directed DNA Polymerase / Q000737:chemistry*; D019281:Dimerization; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D008854:Microscopy, Electron; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D020349:Surface Plasmon Resonance; D013997:Time Factors; D014764:Viral Proteins / Q000737:chemistry* / Q000502:physiology*
chemical_list: D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins; D011993:Recombinant Fusion Proteins; D014764:Viral Proteins; C085913:gene 2.5 protein, Enterobacteria phage T7; D004247:DNA; C034970:bacteriophage T7 induced DNA polymerase; D004259:DNA-Directed DNA Polymerase