SDS-PAGE profile and biological activity of P128 in zymogram and on live S. aureus cells. (a) SDS-PAGE profile of P128. Lane 1: molecular weight marker (97.5-14 kDa), Lane 2: purified P128 (5 μg). (b) Zymogram of purified P128 (5 μg) on autoclaved S. aureus RN4220 cells. Muralytic activity of P128 is seen as a clear zone. (c) Varying concentrations of P128 was added to log-phase cells of MRSA B911 to evaluate biological activity on live cells. P128 was lethal at low (ng) concentrations. A 100-fold higher concentration of Lys16 was required for comparable activity.