title: Insertion of OEP14 into the outer envelope membrane is mediated by proteinaceous components of chloroplasts.
abstract: Most chloroplastic outer envelope membrane proteins are synthesized in the cytosol at their mature size without a cleavable targeting signal. Their insertion into the outer membrane is insensitive to thermolysin pretreatment of chloroplasts and does not require ATP. The insertion has been assumed to be mediated by a spontaneous mechanism or by interaction solely with the lipid components of the outer membrane. However, we show here that insertion of an outer membrane protein requires some trypsin-sensitive and some N-ethylmaleimide-sensitive components of chloroplasts. Association and insertion of the outer membrane protein are saturable and compete with the import of another outer membrane protein. These data suggest that import of chloroplastic outer membrane proteins occurs at specific proteinaceous sites on chloroplasts.
authors.affiliation: Graduate Institute of Life Sciences, National Defense Medical Center, Taipei 112, Taiwan.
authors.forename: S L
authors.initials: SL
authors.lastname: Tu
authors.forename: H M
authors.initials: HM
authors.lastname: Li
mesh_terms: D002736:Chloroplasts / Q000502:physiology*; D003001:Cloning, Molecular; D003600:Cytosol / Q000378:metabolism; D004926:Escherichia coli; D007425:Intracellular Membranes / Q000502:physiology*; D007700:Kinetics; D008563:Membrane Lipids / Q000378:metabolism; D008565:Membrane Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D018532:Pisum sativum / Q000502:physiology*; D010940:Plant Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000302:isolation & purification / Q000378:metabolism; D013820:Thermolysin; D014357:Trypsin
chemical_list: D008563:Membrane Lipids; D008565:Membrane Proteins; D010940:Plant Proteins; D011994:Recombinant Proteins; C077957:OM14 protein, Pisum sativum; D014357:Trypsin; D013820:Thermolysin