Analysis of the gene cluster involved in production and immunity of the peptide antibiotic AS-48 in Enterococcus faecalis.

A region of 7.8 kb of the plasmid pMB2 from Enterococcus faecalis S-48 carrying the information necessary for production and immunity of the peptide antibiotic AS-48 has been cloned and sequenced. It contains the as-48A structural gene plus five open reading frames (as-48B, as-48C, as-48C1, as-48D and as-48D1). Besides As-48D, all the predicted gene products are basic hydrophobic proteins with potential membrane-spanning domains (MSDs). None of them shows any homology with protein sequences stored in databanks, except for As-48D, which shows similarity to the C-terminal domain of ABC transporters and contains a highly conserved ATP-binding site. The gene products of as-48B, as-48C, as-48C1 and as-48D are thought to be involved in AS-48 production and secretion. The only gene able to provide resistance to AS-48 by itself is as-48D1. Immunity also seems to be enhanced at least by the products of as-48B, as-48C1 and as-48D genes. Transcription analysis using probes derived from the different ORFs revealed two large (3.5 and 2.7kb) mRNAs, suggesting that the different genes are organized in two constitutive operons.