TRANSCRIPTIONAL ANALYSIS AND HETEROLOGOUS EXPRESSION OF THE GENE ENCODING BETA-LACTAMASE INHIBITOR PROTEIN (BLIP) FROM STREPTOMYCES-CLAVULIGERUS

Transcription of bli, the gene encoding beta-lactamase (Bla) inhibitor protein (BLIP) of Streptomyces clavuligerus, was analyzed by promoter -probe studies, Northern hybridization and high-resolution S1 nuclease mapping. The 1-kb Sall DNA fragment immediately upstream from the bli open reading frame (ORF) showed promoter activity when tested using t he xylE-based promoter-probe vector, pIJ4083. The promoter activity wa s approx. 36-fold higher in S. clavuligerus us than in S. lividans. No rthern hybridization analysis of S. clavuligerus us RNA revealed that bli was expressed as a 0.7-kb monocistronic transcript. High-resolutio n S1 nuclease mapping identified the transcription start point as an A residue 47 bp upstream from the bli start codon. When the bli ORF, al ong with 111 bp of upstream sequence including the promoter, was intro duced into S. lividans, the transformants produced BLIP, but in amount s approx. 12-fold lower than that produced by S. clavuligerus. Involve ment of some additional regulatory element that is present in S. clavu ligerus us, but absent in S. lividans, could explain the difference in the promoter activities and therefore the difference in the overall e xpression of bli in the two hosts.