title: Properties of the A and A proteins of bacteriophage G4. The origin of G4 replicative-form DNA replication.
abstract: The A and A proteins of the bacteriophage G4 have been purified. The proteins have been analysed for their enzymatic activities on single-stranded and double-stranded DNA. The A protein introduces a single-stranded break at a specific place in the G4 replicative form I DNA. This cleavage site has been localized between nucleotides 506 and 507 in the viral (+) strand. The A protein binds covalently to the 5' end of the cleavage site. The A protein initiates the replication of the viral (+) DNA [Borrias, et al. (1979) Virology, 31, 288-298]; the cleavage site therefore identifies the origin of replication. The A protein cleaves viral (+) strand DNA at many different sites and also binds covalently to the 5' ends of the nick sites. The properties of both proteins strongly resemble the properties of the A and A proteins of the related and much butter analysed phage phi X174. These results indicate that the G4 and phi X174A and A proteins have comparable functions and also that both phages initiate the replicative form DNA in a similar way.
mesh_terms: D001483:Base Sequence; D003090:Coliphages / Q000378:metabolism*; D004261:DNA Replication; D004277:DNA, Single-Stranded / Q000096:biosynthesis*; D004279:DNA, Viral / Q000096:biosynthesis*; D004720:Endonucleases / Q000378:metabolism; D008970:Molecular Weight; D014764:Viral Proteins / Q000378:metabolism*; D014779:Virus Replication
chemical_list: D004277:DNA, Single-Stranded; D004279:DNA, Viral; D014764:Viral Proteins; D004720:Endonucleases