Interacting cytoplasmic loops of subunits a and c of Escherichia coli F sub( 1)F sub( 0) ATP synthase gate H+ transport to the cytoplasm

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 111; no. 47; p. 16730
• Main Authors: Steed, P Ryan, Kraft, Kaitlin A, Fillingame, Robert H
• Format: Journal Article
• Language: English
• Published: 01-11-2014
• Subjects: Escherichia coli
• ISSN: 0027-8424

H+-transporting ... ATP synthase catalyzes the synthesis of ATP via coupled rotary motors within F0 and F1. H+ transport at the subunit a-c interface in transmembranous F0 drives rotation of a cylindrical c10 oligomer within the membrane, which is coupled to rotation of subunit ... within the ... sector of F1 to mechanically drive ATP synthesis. ... functions in a reversible manner, with ATP hydrolysis driving H+ transport. ATP-driven H+ transport in a select group of cysteine mutants in subunits a and c is inhibited after chelation of Ag+ and/or Cd... with the substituted sulfhydryl groups. The H+ transport pathway mapped via these Ag+(Cd...)-sensitive Cys extends from the transmembrane helices (TMHs) of subunits a and c into cytoplasmic loops connecting the TMHs, suggesting these loop regions could be involved in gating H+ release to the cytoplasm. Here, using select loop-region Cys from the single cytoplasmic loop of subunit c and multiple cytoplasmic loops of subunit a, we show that Cd... directly inhibits passive H+ transport mediated by F0 reconstituted in liposomes. Further, in extensions of previous studies, we show that the regions mediating passive H+ transport can be cross-linked to each other. We conclude that the loop-regions in subunits a and c that are implicated in H+ transport likely interact in a single structural domain, which then functions in gating H+ release to the cytoplasm. (ProQuest: ... denotes formulae/symbols omitted.)