Direct observation of stepped proteolipid ring rotation in E. coli FoF1-ATP synthase

Journal article

Although single-molecule experiments have provided mechanistic insight for several molecular motors, these approaches have proved difficult for membrane bound molecular motors like the FoF1-ATP synthase, in which proton transport across a membrane is used to synthesize ATP. Resolution of smaller steps in Fo has been particularly hampered by signal-to-noise and time resolution. Here, we show the presence of a transient dwell between Fo subunits a and c by improving the time resolution to 10 μs at unprecedented S/N, and by using Escherichia coli FoF1 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 Fo motor where c-ring rotational diffusion is limited to 36°.

Authors: Ishmukhametov, R; Hornung, T; Spetzler, D; Frasch, WD

• Publication status: Published
• Publisher: EMBO Press
• Journal: The EMBO Journal
• Volume: 29
• Issue: 23
• Pages: 3911-3923
• Place of publication: England
• Publication date: 2010-10-29
• Acceptance date: 2010-09-21
• DOI: 10.1038/emboj.2010.259
• EISSN: 1460-2075
• ISSN: 0261-4189
• Pmid: 21037553
• Language: English
• Keywords: diffusion; protons; nanotubes; Escherichia coli; amino acid sequence; proton-translocating ATPases; sequence alignment; lipid bilayers; molecular sequence data; proteolipids; mutation