Solution structure of the transmembrane H+-transporting subunit c of the F1F0 ATP synthase

Mark E. Girvin, Vinit K. Rastogi, Frits Abildgaard, John L. Markley, Robert H. Fillingame

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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(Nα), and 43 hydrogen-bonding NMR- derived restraints. The root mean squared deviation for the backbone atoms of the two transmembrane helices was 0.63 Å. 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°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 F(o) 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.

Original languageEnglish (US)
Pages (from-to)8817-8824
Number of pages8
JournalBiochemistry
Volume37
Issue number25
DOIs
StatePublished - Jun 23 1998

ASJC Scopus subject areas

  • Biochemistry

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    Girvin, M. E., Rastogi, V. K., Abildgaard, F., Markley, J. L., & Fillingame, R. H. (1998). Solution structure of the transmembrane H+-transporting subunit c of the F1F0 ATP synthase. Biochemistry, 37(25), 8817-8824. https://doi.org/10.1021/bi980511m