Open AccessA unique loop in T7 DNA polymerase mediates the binding of helicase-primase, DNA binding protein, and processivity factor
Author(s) -
Samir M. Hamdan,
Boriana Marintcheva,
Timothy E. Cook,
SeungJoo Lee,
Stanley Tabor,
Charles C. Richardson
Publication year - 2005
Publication title -
proceedings of the national academy of sciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.0501637102
Subject(s) - primase , replisome , processivity , dna polymerase , dna polymerase ii , biology , dna clamp , helicase , hmg box , dna replication , dna polymerase i , microbiology and biotechnology , dna , seqa protein domain , prokaryotic dna replication , dna binding domain , single stranded binding protein , b3 domain , polymerase , dna binding protein , biochemistry , circular bacterial chromosome , gene , eukaryotic dna replication , transcription factor , reverse transcriptase , rna
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.
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