An erythromycin-resistance gene from an erythromycin-producing strain of Arthrobacter sp

A gene (ermA) coding for a presumed erythromycin-resistance (ErR) determinant from an Er-producing Arthrobacter sp. strain (NRRLB3381) was isolated from a gene bank in phage vector lambda 2001 by probing with a Streptomyces ErR gene. Strongly hybridizing fragments were subcloned and the appropriate segments sequenced. The ermA gene is 76 mol% G + C in content and specifies a protein of 340 aa with an Mr of 37454. S1 nuclease mapping and primer extension identified the putative promoter, which resembles the consensus sequence of Escherichia coli promoters particularly in the -10 region. A potential ribosome-binding site (RBS) (AGGAG) was also located. Unexpectedly, the majority of in vivo ermA transcripts detected were only 245 nt long, suggesting that expression of ErR may be regulated post-transcriptionally. Substantial homology is observed between the predicted aa sequences of the ermA-coded protein and the products of three other ErR determinants, from organisms that do not produce Er.