Catabolite translational effects on the lac messenger RNA of Escherichia coli K12.

The transcriptional and translational events occurring during the induction of the lac operon, were separated by blocking the translational step, either by aminoacid starvation or by addition of chloramphenicol. It was found that the carbon source used during the subsequent translation, affected the rate of beta-galactosidase synthesis. A decoordination effect on the production of enzymes of the lac system was also observed in high catabolite repression media, as well as in nitrogen limiting conditions. These findings suggested a similarity with the polarity phenomenon. In order to test this similarity, polarity suppressors of a Z- polar mutant were isolated. In one of these mutants, probably suA like, no carbon source effect was observed during the translational step. The induction kinetics in different media, after distinct pregrowth conditions, supported the idea that this mutant could be considered catabolite repression resistant only in certain restrictive conditions.