Close linkage between ochre and missense suppressors in Escherichia coli.

It was previously shown that the ochre suppressor mutation sup15B in Escherichia coli determines the accumulation of altered 30S ribosomal subunits and the presence of altered transfer ribonucleic acid (tRNA) capable of suppressing in vitro the UAG codon. This mutation has been mapped in the present study by means of conjugation and transduction experiments. After establishing the location of sup15B near argH, the following order was determined for the markers tested: metB-argH-(sup15B, supA36)-rif-thi. A comparison of location, growth rate, and suppressor pattern determined by sup15B and supM indicates the high probability that both suppressor mutations are identical. This study has also yielded a more precise location for the rifampin resistance gene. The most interesting finding is the very close (if not adjacent) location of the suppressor mutations sup15B and supA36, both of which determine tRNA alterations.