title: A second thylakoid membrane-localized Alb3/OxaI/YidC homologue is involved in proper chloroplast biogenesis in Arabidopsis thaliana.
abstract: The integral membrane proteins Alb3, OxaI, and YidC belong to an evolutionary conserved protein family mediating protein insertion into the thylakoid membrane of chloroplasts, the inner membrane of mitochondria, and bacteria, respectively. Whereas OxaI and YidC are involved in the insertion of a wide range of membrane proteins, the function of Alb3 seems to be limited to the insertion of a subset of the light-harvesting chlorophyll-binding proteins. In this study, we identified a second chloroplast homologue of the Alb3/OxaI/YidC family, named Alb4. Alb4 is almost identical to the Alb3/OxaI/YidC domain of the previously described 110-kDa inner envelope protein Artemis. We show that Alb4 is expressed as a separate 55-kDa protein and that Artemis was identified mistakenly. Alb4 is located in the thylakoid membrane of Arabidopsis thaliana chloroplasts. Analysis of an Arabidopsis mutant (Salk_136199) and RNA interference lines with a reduced level of Alb4 revealed chloroplasts with an altered ultrastructure. Mutant plastids are larger and more spherical in appearance, and the grana stacks within the mutant lines are less appressed than in the wild-type chloroplasts. These data indicate that Alb4 is required for proper chloroplast biogenesis.
authors.affiliation: Department für Biologie I, Botanik, Ludwig-Maximilians-Universität, 80638 München, Germany.
authors.forename: Lars
authors.initials: L
authors.lastname: Gerdes
authors.forename: Thomas
authors.initials: T
authors.lastname: Bals
authors.forename: Eva
authors.initials: E
authors.lastname: Klostermann
authors.forename: Monique
authors.initials: M
authors.lastname: Karl
authors.forename: Katrin
authors.initials: K
authors.lastname: Philippar
authors.forename: Mark
authors.initials: M
authors.lastname: Hünken
authors.forename: Jürgen
authors.initials: J
authors.lastname: Soll
authors.forename: Danja
authors.initials: D
authors.lastname: Schünemann
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000502:physiology*; D002736:Chloroplasts / Q000378:metabolism*; D008565:Membrane Proteins / Q000502:physiology; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D009154:Mutation; D010957:Plasmids / Q000378:metabolism; D017434:Protein Structure, Tertiary; D011523:Protoplasts / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D020524:Thylakoids / Q000378:metabolism*
chemical_list: C106404:ALBINO 3 protein, Arabidopsis; C465629:ARTEMIS protein, Arabidopsis; C512059:Alb4 protein, Arabidopsis; D029681:Arabidopsis Proteins; D008565:Membrane Proteins