Role of TMS5: staphylococcal multidrug-efflux protein QacA.

Background: QacA, a main exporter mediating the multidrug-resistance of Staphylococcus aureus to a variety of antiseptics and disinfectants, possesses a topology of 14 alpha-helical transmembrane segments (TMS). Our study aimed to determine the importance and topology of amino acid residues in and flanking the cytoplasmic end of TMS5.

Methods: Site-directed mutagenesis was used to mutate 5 residues, including L146, A147, V148, W149 and S150, into cysteine.