title: The thylakoid membrane protein ALB3 associates with the cpSecY-translocase in Arabidopsis thaliana.
abstract: The integration of light-harvesting chlorophyll proteins (LHCPs) into the thylakoid membrane requires the integral thylakoid membrane protein ALB3, a homologue of the bacterial cytoplasmic membrane protein YidC. In bacteria, YidC is associated with the SecY-translocase and facilitates the integration of Sec-dependent proteins into the plasma membrane. In addition, it is also involved in the insertion of Sec-independent proteins. In the present study we demonstrate, in Arabidopsis thaliana, that most ALB3 is a constituent of an oligomeric complex of approx. 180 kDa. In addition, we detected ALB3 in several higher-molecular-mass complexes (up to 700 kDa). Furthermore, we show that most ALB3 co-fractionates with cpSecY during gel-filtration analysis and blue native gel electrophoresis, suggesting an association of ALB3 with the cpSecY complex. A direct interaction of ALB3 with the cpSecY complex was demonstrated by co-immunoprecipitation experiments using digitonin-solubilized thylakoid membrane proteins and anti-cpSecY or anti-ALB3 antibodies. This result was further confirmed by electron microscopic co-immunolocalization of ALB3 and cpSecY. In addition, an association of ALB3 with the cpSecY complex was demonstrated directly by cross-linking experiments using the chemical cross-linker disuccinimidyl suberate.
authors.affiliation: Institut für Biologie III der RWTH Aachen, Worringerweg 1, 52074 Aachen, Germany.
authors.forename: Eva
authors.initials: E
authors.lastname: Klostermann
authors.forename: Imke
authors.initials: I
authors.lastname: Droste Gen  Helling
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Carde
authors.forename: Danja
authors.initials: D
authors.lastname: Schünemann
mesh_terms: D017360:Arabidopsis / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000378:metabolism*; D060365:Chloroplast Proteins; D002736:Chloroplasts / Q000378:metabolism; D002850:Chromatography, Gel; D003432:Cross-Linking Reagents / Q000494:pharmacology; D018076:DNA, Complementary / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D007150:Immunohistochemistry; D045342:Light-Harvesting Protein Complexes; D008565:Membrane Proteins / Q000378:metabolism*; D008854:Microscopy, Electron; D045322:Photosynthetic Reaction Center Complex Proteins / Q000378:metabolism*; D011233:Precipitin Tests; D011485:Protein Binding; D021381:Protein Transport; D000069816:SEC Translocation Channels; D020524:Thylakoids / Q000378:metabolism*
chemical_list: C106404:ALBINO 3 protein, Arabidopsis; D029681:Arabidopsis Proteins; D060365:Chloroplast Proteins; D003432:Cross-Linking Reagents; D018076:DNA, Complementary; D045342:Light-Harvesting Protein Complexes; D008565:Membrane Proteins; D045322:Photosynthetic Reaction Center Complex Proteins; C000613370:SCY1 protein, Arabidopsis; D000069816:SEC Translocation Channels