PMID:10217794
| Citation |
Taft-Benz, SA and Schaaper, RM (1999) The C-terminal domain of dnaQ contains the polymerase binding site. J. Bacteriol. 181:2963-5 |
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| Abstract |
The Escherichia coli dnaQ gene encodes the 3'-->5' exonucleolytic proofreading (epsilon) subunit of DNA polymerase III (Pol III). Genetic analysis of dnaQ mutants has suggested that epsilon might consist of two domains, an N-terminal domain containing the exonuclease and a C-terminal domain essential for binding the polymerase (alpha) subunit. We have created truncated forms of dnaQ resulting in epsilon subunits that contain either the N-terminal or the C-terminal domain. Using the yeast two-hybrid system, we analyzed the interactions of the single-domain epsilon subunits with the alpha and theta subunits of the Pol III core. The DnaQ991 protein, consisting of the N-terminal 186 amino acids, was defective in binding to the alpha subunit while retaining normal binding to the theta subunit. In contrast, the NDelta186 protein, consisting of the C-terminal 57 amino acids, exhibited normal binding to the alpha subunit but was defective in binding to the theta subunit. A strain carrying the dnaQ991 allele exhibited a strong, recessive mutator phenotype, as expected from a defective alpha binding mutant. The data are consistent with the existence of two functional domains in epsilon, with the C-terminal domain responsible for polymerase binding. |
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| Keywords |
Binding Sites; DNA Polymerase III/genetics; DNA Polymerase III/metabolism; DNA Replication; Escherichia coli/enzymology; Escherichia coli Proteins; Exodeoxyribonuclease V; Exodeoxyribonucleases/genetics; Exodeoxyribonucleases/metabolism; Mutation; Peptide Fragments/genetics; Peptide Fragments/metabolism; Protein Binding; Saccharomyces cerevisiae/genetics |
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