The Cytoplasmic Loops of Subunit a of Escherichia coli ATP Synthase May Participate in the Proton Translocating Mechanism.

The Cytoplasmic Loops of Subunit a of Escherichia coli ATP Synthase May Participate in the Proton Translocating Mechanism. Research Abstract Details 

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The Cytoplasmic Loops of Subunit a of Escherichia coli ATP Synthase May Participate in the Proton Translocating Mechanism. Abstract Text:

Subunit a plays a key role in promoting H(+) transport and the coupled rotary motion of the subunit c ring in F(1)F(0)-ATP synthase. H(+) binding and release occur at Asp-61 in the middle of the second transmembrane helix (TMH) of F(0) subunit c. H(+) are thought to reach Asp-61 via aqueous pathways mapping to the surfaces of TMHs 2-5 of subunit a based upon the chemical reactivity of Cys substituted into these helices. Here we substituted Cys into loops connecting TMHs 1 and 2 (loop 1-2) and TMHs 3 and 4 (loop 3-4). A large segment of loop 3-4 extending from loop residue 192 loop to residue 203 in TMH4 at the lipid bilayer surface proved to be very sensitive to inhibition by Ag(+). Cys-161 and -165 at the other end of the loop bordering TMH3 were also sensitive to inhibition by Ag(+). Further Cys substitutions in residues 86 and 93 in the middle of the 1-2 loop proved to be Ag(+)-sensitive. We next asked whether the regions of Ag(+)-sensitive residues clustered together near the surface of the membrane by combining Cys substitutions from two domains and testing for cross-linking. Cys-161 and -165 in loop 3-4 were found to cross-link with Cys-202, -203, or -205, which extend into TMH4 from the cytoplasm. Further Cys at residues 86 and 93 in loop 1-2 were found to cross-link with Cys-195 in loop 3-4. We conclude that the Ag(+)-sensitive regions of loops 1-2 and 3-4 may pack in a single domain that packs at the ends of TMHs 3 and 4. We suggest that the Ag(+)-sensitive domain may be involved in gating H(+) release at the cytoplasmic side of the aqueous access channel extending through F(0).

The Cytoplasmic Loops of Subunit a of Escherichia coli ATP Synthase May Participate in the Proton Translocating Mechanism. Publishing Authors By Initials

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The Cytoplasmic Loops of Subunit a of Escherichia coli ATP Synthase May Participate in the Proton Translocating Mechanism. Journal Published:

PUBLICATION TYPE: Journal Article

Journal: The Journal of biological chemistry

VOLUME: 283

Page Numbers: 13044-52

Journal Abbreviation: J. Biol. Chem.

ISSN: 0021-9258

DAY: 12

MONTH: 03

YEAR: 2008

The Cytoplasmic Loops of Subunit a of Escherichia coli ATP Synthase May Participate in the Proton Translocating Mechanism. Information

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LANGUAGE: eng

NlmUniqueID: 2985121

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AFFILIATION: Department of Biomolecular Chemistry, School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin 53706.

Country: United States

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MEDLINETA: J Biol Chem

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The Cytoplasmic Loops of Subunit a of Escherichia coli ATP Synthase May Participate in the Proton Translocating Mechanism Related Publications

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• Interaction of transmembrane helices in ATP synthase subunit a in solution as revealed by spin label difference NMR.
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