PMID:9642286
| Citation |
Jones, PC, Jiang, W and Fillingame, RH (1998) Arrangement of the multicopy H+-translocating subunit c in the membrane sector of the Escherichia coli F1F0 ATP synthase. J. Biol. Chem. 273:17178-85 |
|---|---|
| Abstract |
The multicopy subunit c of the H+-transporting F1F0 ATP synthase of Escherichia coli is thought to fold across the membrane as a hairpin of two hydrophobic alpha-helices. The conserved Asp61, centered in the second transmembrane helix, is essential for H+ transport. In this study, we have made sequential Cys substitutions across both transmembrane helices and used disulfide cross-link formation to determine the oligomeric arrangement of the c subunits. Cross-link formation between single Cys substitutions in helix 1 provided initial limitations on how the subunits could be arranged. Double Cys substitutions at positions 14/16, 16/18, and 21/23 in helix 1 and 70/72 in helix 2 led to the formation of cross-linked multimers upon oxidation. Double Cys substitutions in helix 1 and helix 2, at residues 14/72, 21/65, and 20/66, respectively, also formed cross-linked multimers. These results indicate that at least 10 and probably 12 subunits c interact in a front-to-back fashion to form a ring-like arrangement in F0. Helix 1 packs at the interior and helix 2 at the periphery of the ring. The model indicates that the Asp61 carboxylate is centered between the helical faces of adjacent subunit c at the center of a four-helix bundle. |
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| Keywords |
Adenosine Triphosphate/biosynthesis; Base Sequence; Cell Membrane/enzymology; Cysteine/genetics; Cysteine/metabolism; Disulfides/metabolism; Escherichia coli/enzymology; Molecular Sequence Data; Mutagenesis, Site-Directed; Oligonucleotides, Antisense; Proton-Translocating ATPases/chemistry; Proton-Translocating ATPases/genetics; Proton-Translocating ATPases/metabolism |
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