title: Solution structure of the transmembrane H+-transporting subunit c of the F1F0 ATP synthase.
abstract: Subunit c is the H+-translocating component of the F1F0 ATP synthase complex. H+ transport is coupled to conformational changes that ultimately lead to ATP synthesis by the enzyme. The properties of the monomeric subunit in a single-phase solution of chloroform-methanol-water (4:4:1) have been shown to mimic those of the protein in the native complex. Triple resonance NMR experiments were used to determine the complete structure of monomeric subunit c in this solvent mixture. The structure of the protein was defined by >2000 interproton distances, 64 (3)JN alpha, and 43 hydrogen-bonding NMR-derived restraints. The root mean squared deviation for the backbone atoms of the two transmembrane helices was 0.63 A. The protein folds as a hairpin of two antiparallel helical segments, connected by a short structured loop. The conserved Arg41-Gln42-Pro43 form the top of this loop. The essential H+-transporting Asp61 residue is located at a slight break in the middle of the C-terminal helix, just prior to Pro64. The C-terminal helix changes direction by 30 +/- 5 degrees at the conserved Pro64. In its protonated form, the Asp61 lies in a cavity created by the absence of side chains at Gly23 and Gly27 in the N-terminal helix. The shape and charge distribution of the molecular surface of the monomeric protein suggest a packing arrangement for the oligomeric protein in the F0 complex, with the front face of one monomer packing favorably against the back face of a second monomer. The packing suggests that the proton (cation) binding site lies between packed pairs of adjacent subunit c.
authors.affiliation: Department of Biomolecular Chemistry, University of Wisconsin Medical School, Madison 53706, USA. girvin@aecom.yu.edu
authors.forename: M E
authors.initials: ME
authors.lastname: Girvin
authors.forename: V K
authors.initials: VK
authors.lastname: Rastogi
authors.forename: F
authors.initials: F
authors.lastname: Abildgaard
authors.forename: J L
authors.initials: JL
authors.lastname: Markley
authors.forename: R H
authors.initials: RH
authors.lastname: Fillingame
mesh_terms: D000595:Amino Acid Sequence; D002247:Carbon Isotopes; D004926:Escherichia coli / Q000201:enzymology; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009587:Nitrogen Isotopes; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods; D017433:Protein Structure, Secondary; D006180:Proton-Translocating ATPases / Q000737:chemistry* / Q000378:metabolism; D012996:Solutions
chemical_list: D002247:Carbon Isotopes; D009587:Nitrogen Isotopes; D012996:Solutions; D006180:Proton-Translocating ATPases