MOLECULAR ANALYSIS OF BETA-LACTAMASES FROM 4 SPECIES OF STREPTOMYCES - COMPARISON OF AMINO-ACID-SEQUENCES WITH THOSE OF OTHER BETA-LACTAMASES

Genes encoding extracellular β-lactamases of Streptomyces badius, Streptomyces cacaoi, Streptomyces fradiae and Streptomyces lavendulae were cloned and mapped in Streptomyces lividans. DNA sequence analysis of the β-lactamase genes revealed a high overall G + C content, ranging from 71 to 75 mol%, with a G + C content of 95 mol% at the third position of the codons for all four genes. The primary structure of the β-lactamases including their signal peptides was deduced. The four β-lactamases exhibited homology to each other and to class A β-lactamases from other bacterial genera. We suggest that Streptomyces β-lactamases are representatives of a superfamily of genes, from which class A β-lactamases of Gram-negative bacteria may have evolved.