Investigating the Conformational Dynamics of the Membrane Enzyme LspA

Abstract

Lipoprotein signal peptidase (LspA) is a key enzyme in the lipoprotein processing pathway and is responsible for cleaving the signal sequence of prolipoproteins. LspA is a membrane embedded enzyme that is hypothesized to undergo conformational changes in order for the transmembrane alpha-helical substrate to enter the active site. As both the enzyme and substrate reside in the bacterial inner membrane, enzyme-lipid interactions likely play a role in modulating these conformational changes. LspA conformation changes upon substrate binding and in different membrane mimics are investigated using electron paramagnetic resonance (EPR). Key residues involved in protein - protein interactions and protein - lipid interactions identified using evolutionary couplings are explored using mutagenesis and differing lipid composition. As LspA has been identified as a good candidate for an antibacterial drug target, these studies will also aid in future structure-guided drug design.