title: A 7-kDa region of the bacteriophage T7 gene 4 protein is required for primase but not for helicase activity.
abstract: Bacteriophage T7 gene 4 protein, purified from phage-infected cells, consists of a mixture of 56- and 63-kDa species that provides helicase and primase activities required for T7 DNA replication. The 56-kDa species has been purified independently of the colinear 63-kDa species. Like a mixture of the two proteins, the 56-kDa protein binds single-stranded DNA in the presence of dTTP, catalyzes DNA-dependent hydrolysis of dTTP, and has helicase activity. In contrast to the mixture, the 56-kDa protein cannot catalyze template-dependent RNA primer synthesis. In the absence of a DNA template, both the 56-kDa protein and the mixture of the two species synthesize low levels of diribonucleotide. A putative "zinc finger" present near the amino terminus of the 63-kDa protein but absent from the 56-kDa protein may play a major role in the recognition of primase sites in the template.
authors.affiliation: Department of Biological Chemistry, Harvard Medical School, Boston, MA 02115.
authors.forename: J A
authors.initials: JA
authors.lastname: Bernstein
authors.forename: C C
authors.initials: CC
authors.lastname: Richardson
mesh_terms: D004265:DNA Helicases / Q000235:genetics*; D019915:DNA Primase; D004926:Escherichia coli / Q000235:genetics*; D005796:Genes; D005814:Genes, Viral; D008958:Models, Molecular; D008970:Molecular Weight; D009690:Nucleic Acid Conformation; D011487:Protein Conformation; D012316:RNA Nucleotidyltransferases / Q000235:genetics*; D013604:T-Phages / Q000235:genetics*; D014764:Viral Proteins / Q000235:genetics* / Q000302:isolation & purification
chemical_list: D014764:Viral Proteins; D019915:DNA Primase; D012316:RNA Nucleotidyltransferases; D004265:DNA Helicases