PlyC is composed of two subunits. PlyCB forms an eight-part ring that normally binds to the Spy cell surface. PlyCA is the enzymatically active subunit that degrades the bacterial cell wall. The PlyCB surface is normally positively charged, and Shen, Barros et al. show that it interacts with phosphatidylserine (PS), which is negatively charged. They propose that PlyCB binds to lipid rafts (shown in green) that are enriched in PS; this causes the membrane to fold around PlyC, which ultimately enters the cell inside a vesicle. These vesicles may fuse with bacteria-containing vesicles, giving PlyC access to intracellular Spy (depicted as brown circles). Alternatively, PlyC may escape the vesicle and interact with and kill Spy that is free in the host cell.