Conservation of the Escherichia coli dnaX programmed ribosomal frameshift signal in Salmonella typhimurium.

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