Figure 1

The E. coli type I signal peptidase substrate-binding site. Pockets defining the binding site of E. coli type I signal peptidase. A) Top view of the molecular surface of E. coli SPase binding site (colored blue) with Cα trace of SPase (blue lines). Pockets that accommodate signal peptide side chains are shown in detail in surrounding views and numbered in accordance to their position along the peptide from the S1 pocket that contains the active-site nucleophile, Ser90. B) Top view of the molecular surface of E. coli SPase binding site (colored blue) with the bound conformation of DsbA precursor peptide as a CPK model. C) Side view of structure in B, rotated by 90°.