A pleiotropic defect of membrane synthesis in a thermosensitive mutant tsC42 of Escherichia coli.

Synthesis of membrane proteins in a thermosensitive mutant of Escherichia coli K12, tsC42, that has a defect in a mechanism of cell cycle-dependent duplication of membrane enzymes was examined by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The cells were labeled differentially with [14C]- and [3H]arginine and the membrane proteins synthesized at nonpermissive and permissive temperatures were compared. The results showed that at the nonpermissive temperature, the syntheses of cytoplasmic membrane proteins and outer membrane proteins were reduced more than 70% and 50%, respectively. No significant accumulation of precursor molecules of membrane proteins at the nonpermissive temperature was detected in pulse-chase experiments. It is therefore assumed that the mutant has a defect in a gene that regulates the biosynthesis of many membrane proteins.