Premium
Precursor protein translocation by the Escherichia coli translocase is directed by the protonmotive force.
Author(s) -
Driessen A.J.
Publication year - 1992
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1002/j.1460-2075.1992.tb05122.x
Subject(s) - chromosomal translocation , chemiosmosis , translocase , escherichia coli , biology , escherichia coli proteins , biochemistry , atp synthase , enzyme , gene
The SecY/E protein of Escherichia coli was coreconstituted with the proton pump bacteriorhodopsin and cytochrome c oxidase yielding proteoliposomes capable of sustaining a protonmotive force (delta p) of defined polarity and composition. Proteoliposomes support the ATP‐ and SecA‐dependent translocation of proOmpA which is stimulated by a delta p, inside acid and positive. delta p of opposite polarity, inside alkaline and negative, suppresses translocation while SecA‐mediated ATP hydrolysis continues unabated. delta psi and delta pH are equally effective in promoting or inhibiting translocation. Membrane‐spanning translocation intermediates move backwards in the presence of a reversed delta p. These results support a model [Schiebel, E., Driessen, A.J.M., Hartl, F.‐U. and Wickner, W. (1991) Cell, 64, 927–939] in which the delta p defines the direction of translocation after ATP hydrolysis has released proOmpA from its association with SecA. The polarity effect of the delta p challenges models involving delta p‐dependent membrane destabilization and provides further evidence for a role of the delta p as driving force in precursor protein translocation.