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Identification and Function of Leash Forming Residues in the FoF1 ATP Synthase Molecular Motor Using Single Molecule Measurements
Author(s) -
Frasch Wayne D,
Martin James L..,
Hudson Jennifer
Publication year - 2012
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.26.1_supplement.959.5
Subject(s) - atp synthase , oxidative phosphorylation , chemistry , protein subunit , atpase , atp hydrolysis , atp synthase gamma subunit , biophysics , chemiosmosis , salt bridge , molecular motor , biochemistry , biology , enzyme , mutant , gene
In single molecule rotation measurements, the transient dwells in the proteolipid ring rotation of E. coli FoF1‐ATP synthase were eliminated by mutation of either aE196L or cR50L to subunit a and subunit c, respectively, of the Fo motor. These data indicate the involvement of these residues in the formation of the Fo motor leash that allows rotary motion of the c‐ring to a limit of ~36° while engaged. The rate of oxidative phosphorylation dependent growth observed with these mutations was about one half of that observed with wild type. The ability of ATPase dependent or NADH‐dependent proton gradient formation across inverted membrane vesicles from E. coli was measured by ACMA quenching. Mutations to either residue aE196 or cR50 that altered the ability to form a salt bridge between these subunits altered the rate and extent of proton gradient formation induced by either ATP or NADH. However, none of these mutations decreased the rate of ATP hydrolysis activity of the FoF1 in the inverted membrane vesicles significantly. These results are consistent with the hypothesis that the ability to form the leash between Fo subunits a and c biases rotation of the c‐ring in the ATP synthesis direction. This work was supported by NIH grant 5R01GM097510 to WDF.