Fig. 1.

Ribbon representation of the B. subtilis SecA protein colored by domain (Left) with the individual domains shown on the Right (PDB ID code 1M6N). They include (N-terminal to C-terminal on SecA): the nucleotide-binding domain-1 (NBD-1) (blue), the preprotein cross-linking domain (PPXD) (gold), the nucleotide-binding domain-2 (NBD-2) (light blue), the central helix subdomain (CH) (green), the helical wing domain (HWD) (dark green), the two helix-finger subdomain (THF) (cyan), and the carboxyl-terminal linker (CTL). The CTL is depicted in red and serves as a model of PhoA signal peptide bound to B. subtilis SecA based on the FRET mapping study of Zhang et al. (21).