Conformational dynamics of bacteriophage T7 DNA polymerase and its processivity factor, Escherichia coli thioredoxin

Barak Akabayov, Sabine R. Akabayov, Seung Joo Lee, Stanley Tabor, Arkadiusz W. Kulczyk, Charles C. Richardson

Research output: Contribution to journalArticlepeer-review

38 Scopus citations


Gene 5 of bacteriophage T7 encodes a DNA polymerase (gp5) responsible for the replication of the phage DNA. Gp5 polymerizes nucleotides with low processivity, dissociating after the incorporation of 1 to 50 nucleotides. Thioredoxin (trx) of Escherichia coli binds tightly (Kd = 5 nM) to a unique segment in the thumb subdomain of gp5 and increases processivity. We have probed the molecular basis for the increase in processivity. A single-molecule experiment reveals differences in rates of enzymatic activity and processivity between gp5 and gp5/trx. Small angle X-ray scattering studies combined with nuclease footprinting reveal two conformations of gp5, one in the free state and one upon binding to trx. Comparative analysis of the DNA binding clefts of DNA polymerases and DNA binding proteins show that the binding surface contains more hydrophobic residues than other DNA binding proteins. The balanced composition between hydrophobic and charged residues of the binding site allows for efficient sliding of gp5/trx on the DNA. We propose a model for trx-induced conformational changes in gp5 that enhance the processivity by increasing the interaction of gp5 with DNA.

Original languageEnglish
Pages (from-to)15033-15038
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number34
StatePublished - 24 Aug 2010
Externally publishedYes


  • Conformational transition
  • DNA replication
  • DNA-protein interactions
  • Gene 5 protein

ASJC Scopus subject areas

  • General


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