Escherichia coli DNA polymerase III subunits and ␥ are produced from one gene, dnaX, by a programmed ribosomal frameshift which generates the C terminal of ␥ within the reading frame. To help evaluate the role of the dispensable ␥, the distribution of and ␥ homologs in several other species and the sequence of the Salmonella typhimurium dnaX were determined. All four enterobacteria tested produce and ␥ homologs. S. typhimurium dnaX is 83% identical to E. coli dnaX, but all four components of the frameshift signal are 100% conserved.

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