SecE

SecE is a small integral membrane protein that is a core component of the bacterial SecYEG translocon, a multi-subunit complex that mediates the Sec-dependent translocation of proteins across the inner membrane and their insertion into the lipid bilayer. In most bacteria, SecYEG forms a channel through which preproteins pass while SecA provides the driving energy for translocation by ATP hydrolysis. SecE associates with SecY and SecG and is important for the stability and proper assembly of the translocon; it also participates in gating movements that accompany polypeptide passage and can influence the organization of the lateral gate that integrates hydrophobic segments into the membrane.

SecE is encoded by the secE gene and is widely conserved among Gram-negative and Gram-positive bacteria. Genetic inactivation or depletion of SecE disrupts SecYEG assembly, reduces translocation efficiency, and often results in accumulation of preproteins and growth defects, underscoring its essential role.

Structurally, SecE is an integral inner membrane protein with one or more transmembrane helices and periplasmic/cytoplasmic regions that contact SecY and SecG. The exact topology can vary among species, but the protein consistently lies at the core of the SecYEG complex.

Evolutionarily, SecE has homologs in the eukaryotic Sec61 complex, where the Sec61 beta subunit serves as a functional counterpart. The SecYEG complex is considered the bacterial counterpart of the eukaryotic Sec61 channel, reflecting a common mechanism for protein translocation across membranes.