CLONING AND SEQUENCE OF A GENE ENCODING MACROTETROLIDE ANTIBIOTIC-RESISTANCE FROM STREPTOMYCES-GRISEUS

A gene (nonR) conferring tetranactin resistance on the macrotetrolide- sensitive strain, Streptomyces lividans TK64. was isolated during a sh otgun cloning experiment, in which chromosomal fragments from Streptom yces griseus were ligated into the vector pIJ699 and then introduced b y transformation into S. lividans TK64. The sequence (3326 bp) of the cloned DNA revealed three complete open reading frames (ORFs) and one incomplete ORF encoded on one strand of the DNA. The nonR gene (design ated here ORFA) encodes a polypeptide of 279 amino acids (M(r) 30610) and contains a putative active site motif, GXSXG, characteristic of se rine proteases and esterases. A functional role for the nonR gene prod uct may involve the inactivation of the antibiotic through hydrolysis of one or more ester linkages in the macrotetrolide ring. The deduced product of the incomplete ORFX lying adjacent to ORFA showed 27.9% seq uence identity with the C-terminal region of rat mitochondrial enoyl-C oA hydratase, and is possibly a macrotetrolide biosynthetic enzyme.