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Direct observation of stepped proteolipid ring rotation in E. coli F o F 1 ‐ATP synthase
Author(s) -
Ishmukhametov Robert,
Hornung Tassilo,
Spetzler David,
Frasch Wayne D
Publication year - 2010
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1038/emboj.2010.259
Subject(s) - biology , atp synthase , rotation (mathematics) , ring (chemistry) , biochemistry , enzyme , chemistry , geometry , mathematics , organic chemistry
Although single‐molecule experiments have provided mechanistic insight for several molecular motors, these approaches have proved difficult for membrane bound molecular motors like the F o F 1 ‐ATP synthase, in which proton transport across a membrane is used to synthesize ATP. Resolution of smaller steps in F o has been particularly hampered by signal‐to‐noise and time resolution. Here, we show the presence of a transient dwell between F o subunits a and c by improving the time resolution to 10 μs at unprecedented S/N, and by using Escherichia coli F o F 1 embedded in lipid bilayer nanodiscs. The transient dwell interaction requires 163 μs to form and 175 μs to dissociate, is independent of proton transport residues aR210 and cD61, and behaves as a leash that allows rotary motion of the c‐ring to a limit of ∼36° while engaged. This leash behaviour satisfies a requirement of a Brownian ratchet mechanism for the F o motor where c‐ring rotational diffusion is limited to 36°.