Hamdan, Samir M.Marintcheva, BorianaCook, TimothyLee, Seung-JooTabor, StanleyRichardson, Charles C.2019-10-052005Hamdan, S. M., B. Marintcheva, T. Cook, S.-J. Lee, S. Tabor, and C. C. Richardson. 2005. “A Unique Loop in T7 DNA Polymerase Mediates the Binding of Helicase-Primase, DNA Binding Protein, and Processivity Factor.” Proceedings of the National Academy of Sciences 102 (14): 5096–5101. https://doi.org/10.1073/pnas.0501637102.0027-84240744-28311091-6490http://nrs.harvard.edu/urn-3:HUL.InstRepos:41483384Bacteriophage T7 DNA polymerase (gene 5 protein, gp5) interacts with its processivity factor, Escherichia coli thioredoxin, via a unique loop at the tip of the thumb subdomain. We find that this thioredoxin-binding domain is also the site of interaction of the phage-encoded helicase/primase (gp4) and ssDNA binding protein (gp2.5). Thioredoxin itself interacts only weakly with gp4 and gp2.5 but drastically enhances their binding to gp5. The acidic C termini of gp4 and gp2.5 are critical for this interaction in the absence of DNA. However, the C-terminal tail of gp4 is not required for binding to gp5 when the latter is bound to a primer/template. We propose that the thioredoxin-binding domain is a molecular switch that regulates the interaction of T7 DNA polymerase with other proteins of the replisome.en-USJournal Article2019-10-0510.1073/pnas.0501637102