Gram-negative bacterial post-translational Sec protein export

A reusable bacterial protein-export module in which SecB carries an unfolded precursor to the SecA ATPase, SecA drives the precursor into the SecYEG protein-conducting channel, optional SecDF associated with YajC uses proton motive force to improve late-stage translocation, and signal peptidase I removes the N-terminal signal peptide. The module models the canonical post-translational route used by Gram-negative bacteria. Cotranslational SRP targeting, YidC-dependent membrane insertion, Tat export of folded proteins, lipoprotein maturation, and outer-membrane secretion are neighboring modules.

The module is not specific to Pseudomonas putida. KT2440 supplies a concrete implementation of every role, and reviewed E. coli SecB, SecA, SecY, SecE, SecG, SecD, SecF, YajC, and LepB provide canonical Gram-negative exemplars for the chaperone, motor, SecYEG channel, SecDF-YajC accessory, and type I signal-peptidase steps. SecDF-YajC is an optional accessory assembly rather than the ATPase motor; ATP hydrolysis belongs to SecA, while the individual contribution of YajC remains unresolved. The PTHR30612:SF0 and PTHR43390:SF1 display labels are misleadingly chloroplast-centered, so this module uses the correctly named parent SecA and signal-peptidase I families instead of those subfamily display labels.