Notarnicola, Stephen M.Mulcahy, Henry L.Lee, JoonsooRichardson, Charles C.2019-10-051997Notarnicola, Stephen M., Henry L. Mulcahy, Joonsoo Lee, and Charles C. Richardson. 1997. “The Acidic Carboxyl Terminus of the Bacteriophage T7 Gene 4 Helicase/Primase Interacts with T7 DNA Polymerase.” Journal of Biological Chemistry 272 (29): 18425–33. https://doi.org/10.1074/jbc.272.29.18425.0021-92581083-351Xhttp://nrs.harvard.edu/urn-3:HUL.InstRepos:41483433The gene 4 proteins of bacteriophage T7 provide both primase and helicase activities at the replication fork. Efficient DNA replication requires that the functions of the gene 4 protein be coordinated with the movement of the T7 DNA polymerase. We show that a carboxyl-terminal domain of the gene 4 protein is required for interaction with T7 DNA polymerase during leading strand DNA synthesis. The carboxyl terminus of the gene 4 protein is highly acidic: of the 17 carboxyl-terminal amino acids 7 are negatively charged. Deletion of the coding region for these 17 residues results in a gene 4 protein that cannot support the growth of T7 phage. The purified mutant gene 4 protein has wild-type levels of both helicase and primase activities; however, DNA synthesis catalyzed by T7 DNA polymerase on a duplex DNA substrate is stimulated by this mutant protein to only about 5% of the level of synthesis obtained with wildtype protein. The mutant gene 4 protein can form hexamers and bind single-stranded DNA, but as determined by native PAGE analysis, the protein cannot form a stable complex with the DNA polymerase. The mutant gene 4 protein can prime DNA synthesis normally, indicating that for lagging strand synthesis a different set of helicase/primase-DNA polymerase interactions are involved. These findings have implications for the mechanisms coupling leading and lagging strand DNA synthesis at the T7 replication fork.en-USJournal Article2019-10-0510.1074/jbc.272.29.18425