Publication Date:
2016-02-20
Description:
There is widespread agreement that the clamp loader of the Escherichia coli replicase has the composition DnaX 3 ’. Two DnaX proteins exist in E. coli , full length and a truncated that is created by ribosomal frameshifting. binds DNA polymerase III tightly; does not. There is a controversy as to whether or not DNA polymerase III holoenzyme (Pol III HE) contains . A three- form of Pol III HE would contain three Pol IIIs. Proponents of the three- hypothesis have claimed that found in Pol III HE might be a proteolysis product of . To resolve this controversy, we constructed a strain that expressed only from a mutated chromosomal dnaX . containing a C-terminal biotinylation tag (-C tag ) was provided in trans at physiological levels from a plasmid. A 2000-fold purification of Pol III* (all Pol III HE subunits except β) from this strain contained one molecule of -C tag per Pol III* assembly, indicating that the dominant form of Pol III* in cells is Pol III 2 2 ’. Revealing a role for in cells, mutants that express only display sensitivity to ultraviolet light and reduction in DNA Pol IV-dependent mutagenesis associated with double-strand-break repair, and impaired maintenance of an F’ episome.
Print ISSN:
0305-1048
Electronic ISSN:
1362-4962
Topics:
Biology
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