Lee, Seung-JooMarintcheva, BorianaHamdan, Samir M.Richardson, Charles C.2019-10-052006Lee, Seung-Joo, Boriana Marintcheva, Samir M. Hamdan, and Charles C. Richardson. 2006. “The C-Terminal Residues of Bacteriophage T7 Gene 4 Helicase-Primase Coordinate Helicase and DNA Polymerase Activities.” Journal of Biological Chemistry 281 (35): 25841–49. https://doi.org/10.1074/jbc.m604602200.0021-92581083-351Xhttp://nrs.harvard.edu/urn-3:HUL.InstRepos:41483422The gene 4 protein of bacteriophage T7 plays a central role in DNA replication by providing both helicase and primase activities. The C-terminal helicase domain is not only responsible for DNA-dependent dTTP hydrolysis, translocation, and DNA unwinding, but it also interacts with T7 DNA polymerase to coordinate helicase and polymerase activities. The C-terminal 17 residues of gene 4 protein are critical for its interaction with the T7 DNA polymerase/thioredoxin complex. This C terminus is highly acidic; replacement of these residues with uncharged residues leads to a loss of interaction with T7 DNA polymerase/thioredoxin and an increase in oligomerization of the gene 4 protein. Such an alteration on the C terminus results in a reduced efficiency in strand displacement DNA synthesis catalyzed by gene 4 protein and T7 DNA polymerase/thioredoxin. Replacement of the C-terminal amino acid, phenylalanine, with non-aromatic residues also leads to a loss of interaction of gene 4 protein with T7 DNA polymerase/ thioredoxin. However, neither of these modifications of the C terminus affects helicase and primase activities. A chimeric gene 4 protein containing the acidic C terminus of the T7 gene 2.5 single-stranded DNA-binding protein is more active in strand displacement synthesis. Gene 4 hexamers containing even one subunit of a defective C terminus are defective in their interaction with T7 DNA polymerase.en-USJournal Article2019-10-0510.1074/jbc.M604602200