Fig. 1. Protein translocation in E. coli.
(A) Jamming of SecY occurs during post-translational translocation of the LamB-LacZ hybrid, resulting in accumulation of precursor proteins such as pMalE (in red) with their signal sequence (in green) still attached. (B) When the hybrid is targeted for co-translational translocation (H*LamB-LacZ), it is secreted into the periplasm. Properties of the LacZ fusion strains are summarized in the text box. (C) Co-translational translocation of a wild-type SRP substrate (purple). (D) During co-translational translocation, antibiotics that inhibit peptide chain elongation jam the translocator. Orange circles; translating ribosome, OM; outer membrane, IM; inner membrane, IMP; IM protein, P; periplasm.