Catabolite repression in Escherichia coli mutants lacking cyclic AMP.

Summary The regulation of catabolite repression of -galactosidase has been studied in Escherichia coli mutants deleted for the adenyl cyclase gene (cya ), and thus unable to synthesize cyclic AMP. It has been found that, provided a second mutation occurs either in the crp gene coding for the catabolite gene activator protein (CAP) or in the Lactose region, these mutants exhibit catabolite repression. If the catabolite repression seen in the mutant strains corresponds to the mechanism operating in wild-type cells, the results would suggest that the intracellular concentration of cyclic AMP cannot be the unique regulator of catabolite repression.Jacques Monod was still with us when most of the work described in this and the following paper was accomplished. His constant interest, his unfailing advice, his warm support, were invaluable. It will be difficult for us to ever enjoy a successful experiment without regretting that he cannot share this pleasure with us.