title: Arginine-induced conformational change in the c-ring/a-subunit interface of ATP synthase.
abstract: The rotational mechanism of ATP synthases requires a unique interface between the stator a subunit and the rotating c-ring to accommodate stability and smooth rotation simultaneously. The recently published c-ring crystal structure of the ATP synthase of Ilyobacter tartaricus represents the conformation in the absence of subunit a. However, in order to understand the dynamic structural processes during ion translocation, studies in the presence of subunit a are required. Here, by intersubunit Cys-Cys cross-linking, the relative topography of the interacting helical faces of subunits a and c from the I. tartaricus ATP synthase has been mapped. According to these data, the essential stator arginine (aR226) is located between the c-ring binding pocket and the cytoplasm. Furthermore, the spatially vicinal residues cT67C and cG68C in the isolated c-ring structure yielded largely asymmetric cross-linking products with aN230C of subunit a, suggesting a small, but significant conformational change of binding-site residues upon contact with subunit a. The conformational change was dependent on the positive charge of the stator arginine or the aR226H substitution. Energy-minimization calculations revealed possible modes for the interaction between the stator arginine and the c-ring. These biochemical results and structural restraints support a model in which the stator arginine operates as a pendulum, moving in and out of the binding pocket as the c-ring rotates along the interface with subunit a. This mechanism allows efficient interaction between subunit a and the c-ring and simultaneously allows almost frictionless movement against each other.
authors.affiliation: Institut für Mikrobiologie, ETH Zürich Hönggerberg, Switzerland.
authors.forename: Thomas
authors.initials: T
authors.lastname: Vorburger
authors.forename: Judith Zingg
authors.initials: JZ
authors.lastname: Ebneter
authors.forename: Alexander
authors.initials: A
authors.lastname: Wiedenmann
authors.forename: Damien
authors.initials: D
authors.lastname: Morger
authors.forename: Gerald
authors.initials: G
authors.lastname: Weber
authors.forename: Kay
authors.initials: K
authors.lastname: Diederichs
authors.forename: Peter
authors.initials: P
authors.lastname: Dimroth
authors.forename: Christoph
authors.initials: C
authors.lastname: von Ballmoos
mesh_terms: D019943:Amino Acid Substitution; D001120:Arginine / Q000737:chemistry*; D025243:Bacterial Proton-Translocating ATPases / Q000032:analysis / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D001665:Binding Sites; D002462:Cell Membrane / Q000378:metabolism; D003300:Copper / Q000737:chemistry; D003432:Cross-Linking Reagents / Q000494:pharmacology; D003545:Cysteine / Q000737:chemistry / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics; D006860:Hydrogen Bonding; D006863:Hydrogen-Ion Concentration; D008051:Lipid Bilayers / Q000737:chemistry; D008958:Models, Molecular; D008968:Molecular Conformation; D009876:Operon; D010084:Oxidation-Reduction; D010957:Plasmids / Q000378:metabolism; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D011522:Protons; D011994:Recombinant Proteins / Q000378:metabolism
chemical_list: D003432:Cross-Linking Reagents; D008051:Lipid Bilayers; D011522:Protons; D011994:Recombinant Proteins; D003300:Copper; D001120:Arginine; D025243:Bacterial Proton-Translocating ATPases; D003545:Cysteine