POSSIBLE INVOLVEMENT OF THE LYSINE EPSILON-AMINOTRANSFERASE GENE (LAT) IN THE EXPRESSION OF THE GENES ENCODING ACV SYNTHETASE (PCBAB) AND ISOPENICILLIN-N SYNTHASE (PCBC) IN STREPTOMYCES-CLAVULIGERUS

Streptomyces clavuligerus produces the beta-lactam antibiotics penicil lin N, O-carbamoyldeacetylcephalosporin C and cephamycin C. We charact erized a wildtype DNA region which restores antibiotic formation to a mutant strain named NP1, previously shown to exhibit depressed activit ies for two early enzymes of cephalosporin synthesis, delta-(L-alpha-a minoadipyl)-L-cysteinyl-D-valine synthetase (ACVS) and isopenicillin N synthase (IPNS). L-Lysine E-aminotransferase (LAT) assays and alpha-A AA feeding experiments suggested that strain NP1 is a lat mutant. NP1 recovered LAT, ACVS and IPNS activities when transformed with the clon ed region. DNA-sequencing showed that this region encodes the entire L AT gene (lat), required for the conversion of L-lysine to the p-lactam precursor L-alpha-aminoadipic acid (alpha-AAA), as well as the upstre am half of the ACVS gene (pcbAB). The activities of ACVS and IPNS appe ar to depend upon LAT expression. Gene fusions constructed to investig ate promoter activities in the cloned region support a model of interd ependence in the expression of the genes for LAT, ACVS and IPNS (pcbC) .