Mutational loss of susceptibility to mutacin GS-5 in Streptococcus pyogenes: surface protein in a tolerant variant.

A variant (S4340) nonsusceptible to mutacin GS-5 was previously obtained from a strain of Streptococcus pyogenes susceptible to this bacteriocin. The variant was found to adsorb as much bacteriocin as parent cells and exhibit similar susceptibility to seven antibiotics and two detergents. Electrophoretic analysis of protein dissociated from mutant cells by brief sonication revealed the presence of a 74,000-dalton polypeptide not discernible in profiles obtained from susceptible parent cells. The precise role of this tolerance-associated marker remains to be determined. The protein does not appear to be an exported product transiently associated with the cell envelope.