Molecular Cloning and Functional Characterization of SecE of a Marine Bacterium,Vibrio alginolyticus

Abstract

SecE is an essential membrane component of theEscherichia coliprotein translocation machinery, which utilizes ATP and the proton motive force as energy sources. ThesecEhomologue of marineVibrio alginolyticus,in which protein translocation requires ATP and the sodium motive force, was cloned, sequenced, and characterized. Unlike most SecE homologues found in various organisms, SecE ofV. alginolyticus(Va-SecE) possesses three transmembrane sequences likeE. coliSecE (Ec-SecE) and complements the ΔsecEmutation ofE. coli.Alignment of the Ec-SecE and Va-SecE sequences revealed that the non-essential N-terminal half was less homologous than the essential C-terminal half between the two SecEs. TheE. colistrain was able to grow and translocate the secretory protein in the complete absence of Ec-SecE when Va-SecE was expressed. The stabilization of SecY overproduction by Va-SecE was as effective as that by Ec-SecE, indicating that Va-SecE interacts withE. coliSecY despite the difference in energy requirement.