A COMMON SYSTEM CONTROLS THE INDUCTION OF VERY DIFFERENT GENES - THE CLASS-A BETA-LACTAMASE OF PROTEUS-VULGARIS AND THE ENTEROBACTERIAL CLASS-C BETA-LACTAMASE

Among the Enterobacteriaceae, Proteus vulgaris is exceptional in the i nducible production of a 29-kDa beta-lactamase (cefuroximase) with an unusually high activity towards the beta-lactamase-stable oximino-ceph alosporins (e.g. cefuroxime and cefotaxime). Sequencing of the corresp onding gene, cumA, showed that the derived CumA beta-lactamase belonge d to the molecular class A. The structural gene was under the direct c ontrol of gene cumR, which was transcribed backwards and whose initiat ion codon was 165 bp away from that of the beta-lactamase gene. This r esembled the arrangement of structural and regulator genes ampC and am pR of the 39-kDa molecular-class-C beta-lactamase AmpC present in many enterobacteria. Moreover, cloned genes ampD and ampG for negative mod ulation and signal transduction of AmpC beta-lactamase induction, resp ectively, were also able to restore constitutively CumA overproducing and non-inducible P. vulgaris mutants to the inducible, wildtype pheno type. The results indicate that controls of the induction phenomena ar e equivalent for the CumA and AmpC beta-lactamase. Very different stru ctural genes can thus be under the control of identical systems.