Characterization of an E. coli mutant with a thermolabile initiation factor IF3 activity.

A thermosensitive E. coli mutant is described which has at least two defects in vitro: a thermolabile initiation factor IF3 activity and a modified L-phenylalanine: tRNAPhe ligase (EC 6.1.1.20) activity. These two defects cotransduce and are located near 38 min on the new E. coli map. Thermoresistant revertants showing in vitro reversion for one defect also revert in vitro for the other defect. The thermosensitive mutation is recessive to its wild type allele, and in vitro analysis of wild type/ mutant heterodiploïds also show reversion for both defects.