Structure determination of the membrane bound protease LspA by NMR spectroscopy

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Lipoprotein signal peptidase II (LspA) is a bacterial protease located in the bacterial membrane. LspA cleaves the signal peptide from prolipoproteins after they are exported across the inner membrane. LspA belongs to an unusual class of aspartic acid proteases with no homologous proteins present in archaea or eukaryotes which makes it an excellent target for the development of new antibiotics. The protein contains 164 amino acids with four predicted alpha-helices. We want to determine the structure of LspA by liquid state NMR spectroscopy and investigate how the cyclic peptide inhibitor globomycin interacts with the protein. We have established expression and labelling protocols using our cell-free expression system and have measured 2D and 3D NMR spectra of LspA in nanodiscs that show very good chemical shift dispersion. The data presented suggest that a full structure determination is possible using the protocol that we have established in the past for the structure determination of the C-terminal domain of presenilin and of Proteorhodopsin.