LIF, THE LYSOSTAPHIN IMMUNITY FACTOR, COMPLEMENTS FEMB IN STAPHYLOCOCCAL PEPTIDOGLYCAN INTERPEPTIDE BRIDGE FORMATION

The formation of the Staphylococcus aureus peptidoglycan pentaglycine interpeptide chain needs FemA and FemB for the incorporation of glycin es Gly2-Gly3, and Gly4-Gly5, respectively. The lysostaphin immunity fa ctor Lif was able to complement FemB, as could be shown by serine inco rporation and by an increase in lysostaphin resistance in the wild-typ e as well as in a femB mutant. However, Lif could not substitute for F emA in femA or in femAB-null mutants. Methicillin resistance, which is dependent on functional FemA and FemB, was not complemented by Lif, s uggesting that serine-substituted side chains are a lesser substrate f or penicillin-binding protein PBP2' in methicillin resistance.