CLONING AND SEQUENCES OF 2 MACROLIDE-RESISTANCE-ENCODING GENES FROM MYCINAMICIN-PRODUCING MICROMONOSPORA-GRISEORUBIDA

Two macrolide-resistance determinants were cloned from a mycinamicin ( Mm)-producing Micromonospora griseo- rubida strain in Streptomyces liv idans and Streptomyces parvulus. One of the cloned genes, designated m yrA, was cloned as a gene which conferred strong resistance to Mm and tylosin (Ty), but not to erythromycin (Er) or josamycin (Jm) on S. liv idans. Another gene, named myrB, was cloned as an Er-R-encoding gene w hich conferred MLS resistance (to macrolide, lincosamide and streptogr amine B antibiotics) on S. parvulus. Both myrA and myrB were sequenced and the corresponding ORFs were determined. The deduced amino acid (a a) sequence of myr A showed no similarity to proteins in the available databases, suggesting that an unknown mechanism of macrolide resistan ce is exerted by the MyrA protein. The deduced aa sequence of myrB exh ibited high similarity to 23S rRNA methyltransferases (MTases), such a s ErmE and CarB, from a variety of microorganisms.