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Kim, YT, Tabor, S, Bortner, C, Griffith, JD and Richardson, CC (1992) Purification and characterization of the bacteriophage T7 gene 2.5 protein. A single-stranded DNA-binding protein. J. Biol. Chem. 267:15022-31

Bacteriophage T7 gene 2.5 protein has been purified to homogeneity from cells overexpressing its gene. Native gene 2.5 protein consists of a dimer of two identical subunits of molecular weight 25,562. Gene 2.5 protein binds specifically to single-stranded DNA with a stoichiometry of approximately 7 nucleotides bound per monomer of gene 2.5 protein; binding appears to be noncooperative. Electron microscopic analysis shows that gene 2.5 protein is able to disrupt the secondary structure of single-stranded DNA. The single-stranded DNA is extended into a chain of gene 2.5 protein dimers bound along the DNA. In fluorescence quenching and nitrocellulose filter binding assays, the binding constants of gene 2.5 protein to single-stranded DNA are 1.2 x 10(6) M-1 and 3.8 x 10(6) M-1, respectively. Escherichia coli single-stranded DNA-binding protein and phage T4 gene 32 protein bind to single-stranded DNA more tightly by a factor of 25. Fluorescence spectroscopy suggests that tyrosine residue(s), but not tryptophan residues, on gene 2.5 protein interacts with single-stranded DNA.

PubMed

Adenosine Triphosphate/metabolism; Amino Acid Sequence; Binding Sites; Cell Line; Chromatography, DEAE-Cellulose; Chromatography, Gel; DNA, Single-Stranded/metabolism; DNA-Binding Proteins/isolation & purification; DNA-Binding Proteins/metabolism; DNA-Binding Proteins/ultrastructure; Electrophoresis, Polyacrylamide Gel; Genes, Viral; Isoelectric Focusing; Microscopy, Electron; Molecular Sequence Data; Molecular Weight; Plasmids; Sequence Alignment; Spectrometry, Fluorescence; T-Phages/genetics; T-Phages/metabolism; Viral Proteins/isolation & purification; Viral Proteins/metabolism; Viral Proteins/ultrastructure