Lanthionine-containing peptide antibiotic (lantibiotic) active on certain Gram-positive bacteria. The bactericidal activity of lantibiotics is based on depolarization of energized bacterial cytoplasmic membranes, initiated by the formation of aqueous transmembrane pores (By similarity). Either cell associated or in a released extracellular form. Maturation of lantibiotics involves the enzymatic conversion of Thr, and Ser into dehydrated AA and the formation of thioether bonds with cysteine. This is followed by membrane translocation and cleavage of the modified precursor (By similarity). There are two genes coding for lantibiotic streptococcin A-M49, their coding sequences only differ in the propeptide region. Belongs to the type A lantibiotic family.