CHARACTERIZATION OF A NEW STAPHYLOCOCCAL GENE, VGAB, ENCODING A PUTATIVE ABC TRANSPORTER CONFERRING RESISTANCE TO STREPTOGRAMIN-A AND RELATED-COMPOUNDS

The Staphylococcus aureus plasmid gene, vgaB, conferring resistance to streptogramin (SgA) and related compounds (PIIA, virginiamycin M, mik amycin A, synergistin A, Dalfopristin) was cloned and sequenced. This gene potentially encodes a 552-aa protein, VgaB, of 61 327 Da, which e xhibits a significant similarity with the ATP-binding domains of numer ous proteins. VgaB has two ATP-binding domains containing each of the A and the B motifs described by Walker et al. [Walker, J.E., Saraste, M., Runswick, M.J., Gay, N.J., 1982. Distantly related sequences in th e alpha-and beta-subunits of ATP synthase, myosin, kinases and other A TP-requiring enzymes and a common nucleotide binding fold. EMBO J., 1, 945-951], but does not include TM hydrophobic domains. The 155-amino- acid sequence between the two ATP-binding domains of VgaB is richer in Glu than the rest of the protein. The vgaB gene was found in 21 of th e 52 SgA(R) and independent wt staphylococci investigated. In each of the 21 staphylococci, vgaB was carried on a plasmid of 50-90 kb also h arboring the vatB gene encoding an acetyltransferase inactivating SgA. In all plasmids, vgaB and vatB have the same relative positions. (C) 1997 Elsevier Science B.V.