Cleavage of a Multispanning Membrane Protein by an Intramembrane Serine Protease†

摘要

All intramembrane proteases are known to cleave membrane proteins with a single transmembranenhelix. Such cleavages often release anchored soluble domains, which play a role in physiologicallynimportant inter- and intracellular processes. However, in many cases the physiological roles/substrates ofnintramembrane proteases are not known. It is interesting that no multispanning substrates were identified sonfar, despite the fact that intramembrane proteases have promiscuous substrate recognition and cleavagencapabilities. Here we determined whether, in a synthetic experimental system, intramembrane proteases haventhe capability to interact with and cleave multispanning membrane proteins. We utilized the Escherichia colinrhomboid GlpG, an intramembrane serine protease, and truncated versions of the E. coli multidrugntransporter MdfA as model multispanning membrane proteins. On the basis of in vivo and in vitro studiesnon the association of GlpG with various MdfA constructs and their cleavage, we conclude that GlpG is able tonrecognize and cleave truncated forms of MdfA but not the intact protein. We propose that GlpG has thencapacity to act on unfolded multispanning membrane proteins, thus providing an incentive for investigatingnpossible physiological consequences.