Structural studies on the intact and the soluble C‐terminal region of E. Coli signal peptidase, a membrane protein

Abstract

High resolution NMR data have been obtained from full-length E. Coli signal peptidase (37kD), a membrane protein, in detergent micelles and are compared with data from the large soluble C-terminal fragment (28kD). Signal peptidase is a critical component of protein transport processes. Exported preproteins are differentiated from cytosolic proteins by an amino-terminal signal peptide that is recognized by the transport machinery. Once the preprotein is translocated across the membrane, signal peptidase cleaves off the signal peptide, and the preprotein is free to fold and perform its function. We were able to partially assign the deuturated, 15N and 13C labeled signal peptidase in dodecylphosphocholine (DPC) micelles using experiments including HSQC-TROSY, HN(CO), HNCACB, HNCA and HN(CO)CA. We find that it is feasible to obtain some structural information for the 37kDa protein in micelles. The complete 3D structure for the soluble C-terminal signal peptidase, labeled with 15N and 13C, is being determined from HSQC-NOESY, HN(CO), HNCACB, and CBCA(CO)NH experiments. This research was supported in part by NIH: GM37639 (D.A.K.) and GM65250 (P.L.Y.)