A SecA-associated protease modulates the extent of surface display of staphylococcal protein A

The "signal hypothesis" proposed that N-terminal sequences of secretory proteins contain targeting cues directing nascent polypeptides to the endoplasmic reticulum. This concept was later confirmed as broadly applicable, even to prokaryotes with a single membrane. In gram-positive bacteria, signal sequences bearing the YSIRK/GXXS motif are necessary and sufficient to direct precursors to septal membranes. However, trans-acting factors involved in this spatially restricted targeting remain largely unknown. Here, we identify a member of the M20 metalloprotease family as a potential contributor to the septal surface display of proteins containing YSIRK/GXXS signal peptides.