The thioredoxin binding domain of bacteriophage T7 DNA polymerase confers processivity on Escherichia coli DNA polymerase I.


Bacteriophage T7 DNA polymerase shares extensive sequence homology with Escherichia coli DNA polymerase I. However, in vivo, E. coli DNA polymerase I is involved primarily in the repair of DNA whereas T7 DNA polymerase is responsible for the replication of the viral genome. In accord with these roles, T7 DNA polymerase is highly processive while E. coli DNA polymerase I has low processivity. The high processivity of T7 DNA polymerase is achieved through tight binding to its processivity factor, E. coli thioredoxin. We have identified a unique 76-residue domain in T7 DNA polymerase responsible for this interaction. Insertion of this domain into the homologous site in E. coli DNA polymerase I results in a dramatic increase in the processivity of the chimeric DNA polymerase, a phenomenon that is dependent upon its binding to thioredoxin.



Nucleotide Incorporation, Historical Protein Properties (MW, pI, ...), Exonuclease Activity


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Polymerase Reference Property Result Context
Klenow fragment Bedford E1997 Processivity 20bp
Klenow fragment Bedford E1997 Specific Activity 2200 Other Technique: Polymerase Assay (M13 DNA)
T7 Bedford E1997 3-5' Exonuclease (proofreading) Yes
T7 Bedford E1997 Processivity 300bp
T7 Bedford E1997 Specific Activity 1E+04 units/mg Technique: Polymerase Assay (M13 DNA)
Klenow-TBD Bedford E1997 Processivity 300bp
Klenow-TBD Bedford E1997 Specific Activity 3400 units/mg Technique: Polymerase Assay (M13 DNA)

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