title: Chloroplast SecE: evidence for spontaneous insertion into the thylakoid membrane.
abstract: SecE, an essential component of the bacterial SecAYEG translocase, mediates protein translocation across the cytoplasmic membrane. In the thylakoid membranes of chloroplasts an SecE homologue, cpSecE, has recently been identified. In this report we show that insertion of cpSecE does not require stromal extract, indicating that signal recognition particle is not involved. Removal of nucleoside triphosphates has apparently no effect on the integration, again ruling out an involvement of SRP or its partner protein, FtsY. The use of well-known inhibitors of the Sec- and Tat pathways, sodium azide and nigericin, respectively, also had no influence on membrane insertion. The data presented here point towards cpSecE as another passenger of a wholly spontaneous import/insertion pathway in the thylakoids of chloroplasts.
authors.affiliation: Institut für Biochemie und Molekulare Zellbiologie der Universität Wien, Ludwig-Boltzmann-Forschungsstelle für Biochemie, Dr. Bohrgasse 9, A-1030 Vienna, Austria.
authors.forename: Jürgen M
authors.initials: JM
authors.lastname: Steiner
authors.forename: Thomas
authors.initials: T
authors.lastname: Köcher
authors.forename: Christine
authors.initials: C
authors.lastname: Nagy
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Löffelhardt
mesh_terms: D029681:Arabidopsis Proteins / Q000737:chemistry / Q000378:metabolism*; D002736:Chloroplasts / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000378:metabolism*; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism; D008958:Models, Molecular; D021381:Protein Transport; D000069816:SEC Translocation Channels; D018724:Spinacia oleracea / Q000378:metabolism; D020524:Thylakoids / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D029968:Escherichia coli Proteins; D008565:Membrane Proteins; D000069816:SEC Translocation Channels; C065493:SecE protein, E coli