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A unique loop in T7 DNA polymerase mediates the binding of helicase-primase, DNA binding protein, and processivity factor.

ABSTRACT: Bacteriophage 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.

SUBMITTER: Hamdan SM

PROVIDER: S-EPMC556000 | biostudies-literature | 2005 Apr

REPOSITORIES: biostudies-literature

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A unique loop in T7 DNA polymerase mediates the binding of helicase-primase, DNA binding protein, and processivity factor.

Hamdan Samir M SM Marintcheva Boriana B Cook Timothy T Lee Seung-Joo SJ Tabor Stanley S Richardson Charles C CC

Proceedings of the National Academy of Sciences of the United States of America 20050328 14

Bacteriophage 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 ...[more]

PMID: 15795374

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