tgs and crr : Genes involved in catabolite inhibition and inducer exclusion in Escherichia coli

We recently described some properties of mutants of Escherichia coli that had been selected as being resistant to the growth inhibitory effects of 5-thio-Dglucose [l]. These mutants still grew on glucose, albeit at only half the rate at which the wild-type organisms grew, but glucose was no longer utilized in preference to other sugars taken up via the phosphoenolpyruvate-dependent phosphotransferase (PT) system; they were thus altered in ‘catabolite inhibition’ 121. A further chara~te~stic of these mutants was that they were strongly impaired in their ability to adapt to grow on media containing salts of Cqdicarboxylic acids as sole carbon source, but that this impairment was overcome by the addition of adenosine 3’,5’-cyclic phosphate (CAMP); as expected from this finding, the adenylate cyclase activity [3] of toluenized suspensions of the mutants was much less than that of similarly treated wild-type organisms. We had previously [4] described the isolation of mutants that had lost the property of ‘inducer exclusion’ [5]; such mut~ts readily adapted to grow on sugars not taken up through the PT-system even in the absence of the enzyme I (PtsI) or HPr (pts&) components of the PT-system. Both the loss of ‘catabolite inhibition’ and the loss of ‘inducer exclusion’ were co-transducible with ptsl; however, even the evidence then available [l] indicated that more than one gene was involved. It is the purpose of this paper to report that there are two genes concerned and to summarize some properties of organisms mutated in them. One gene, mapping between cys.4 and p&I [6] and very close to if not identical with p&T, specifies ‘catabolite inhibi-