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, mikamycin A, synergistin A, Dalfopristin) was cloned and sequenced. This gene potentially encodes a 552-aa protein, VgaB, of 61 327 Da, which exhibits a significant similarity with the ATP-binding domains of numerous 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 the α- and β-subunits of ATP synthase, myosin, kinases and other ATP-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 the 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 harboring the vatB gene encoding an acetyltransferase inactivating SgA. In all plasmids, vgaB and vatB have the same relative positions.