Substrate engagement by the intramembrane metalloprotease SpoIVFB.

S2P intramembrane metalloproteases regulate diverse signaling pathways across all three domains of life. However, the mechanism by which S2P metalloproteases engage substrates and catalyze peptide hydrolysis within lipid membranes has remained elusive. Here we determine the cryo-EM structure of the S2P family intramembrane metalloprotease SpoIVFB from Bacillus subtilis bound to its native substrate Pro-σ.