title: Carbonic anhydrase subunits form a matrix-exposed domain attached to the membrane arm of mitochondrial complex I in plants.
abstract: Complex I of Arabidopsis includes five structurally related subunits representing gamma-type carbonic anhydrases termed CA1, CA2, CA3, CAL1, and CAL2. The position of these subunits within complex I was investigated. Direct analysis of isolated subcomplexes of complex I by liquid chromatography linked to tandem mass spectrometry allowed the assignment of the CA subunits to the membrane arm of complex I. Carbonate extraction experiments revealed that CA2 is an integral membrane protein that is protected upon protease treatment of isolated mitoplasts, indicating a location on the matrix-exposed side of the complex. A structural characterization by single particle electron microscopy of complex I from the green alga Polytomella and a previous analysis from Arabidopsis indicate a plant-specific spherical extra-domain of about 60 A in diameter, which is attached to the central part of the membrane arm of complex I on its matrix face. This spherical domain is proposed to contain a heterotrimer of three CA subunits, which are anchored with their C termini to the hydrophobic arm of complex I. Functional implications of the complex I-integrated CA subunits are discussed.
authors.affiliation: Institut für Angewandte Genetik, Universität Hannover, Herrenhäuser Strasse 2, D-30419 Hannover, Germany.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Sunderhaus
authors.forename: Natalya V
authors.initials: NV
authors.lastname: Dudkina
authors.forename: Lothar
authors.initials: L
authors.lastname: Jänsch
authors.forename: Jennifer
authors.initials: J
authors.lastname: Klodmann
authors.forename: Jesco
authors.initials: J
authors.lastname: Heinemeyer
authors.forename: Mariano
authors.initials: M
authors.lastname: Perales
authors.forename: Eduardo
authors.initials: E
authors.lastname: Zabaleta
authors.forename: Egbert J
authors.initials: EJ
authors.lastname: Boekema
authors.forename: Hans-Peter
authors.initials: HP
authors.lastname: Braun
mesh_terms: D017360:Arabidopsis / Q000201:enzymology*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D002256:Carbonic Anhydrases / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D002478:Cells, Cultured; D000460:Chlorophyta / Q000201:enzymology; D042967:Electron Transport Complex I / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism; D046529:Microscopy, Electron, Transmission; D008928:Mitochondria / Q000737:chemistry / Q000201:enzymology*; D024101:Mitochondrial Proteins / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure; D010447:Peptide Hydrolases; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D008565:Membrane Proteins; D024101:Mitochondrial Proteins; D021122:Protein Subunits; D010447:Peptide Hydrolases; C000608070:CAL1 protein, Arabidopsis; C000608071:CAL2 protein, Arabidopsis; D002256:Carbonic Anhydrases; D042967:Electron Transport Complex I