Dataset Information

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

ABSTRACT: 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?F?-ATP synthase, in which proton transport across a membrane is used to synthesize ATP. Resolution of smaller steps in F? has been particularly hampered by signal-to-noise and time resolution. Here, we show the presence of a transient dwell between F? subunits a and c by improving the time resolution to 10 ?s at unprecedented S/N, and by using Escherichia coli F?F? embedded in lipid bilayer nanodiscs. The transient dwell interaction requires 163 ?s to form and 175 ?s 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? motor where c-ring rotational diffusion is limited to 36°.

SUBMITTER: Ishmukhametov R

PROVIDER: S-EPMC3020647 | biostudies-literature | 2010 Dec

REPOSITORIES: biostudies-literature

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Direct observation of stepped proteolipid ring rotation in E. coli F₀F₁-ATP synthase.

Ishmukhametov Robert R Hornung Tassilo T Spetzler David D Frasch Wayne D WD

The EMBO journal 20101029 23

Although single-molecule experiments have provided mechanistic insight for several molecular motors, these approaches have proved difficult for membrane bound molecular motors like the F₀F₁-ATP synthase, in which proton transport across a membrane is used to synthesize ATP. Resolution of smaller steps in F₀ has been particularly hampered by signal-to-noise and time resolution. Here, we show the presence of a transient dwell between F₀ subunits a and c by improving the time resolution to 10 μs at ...[more]

PMID: 21037553

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Project description:The proton-driven ATP synthase (FOF1) is comprised of two rotary, stepping motors (FO and F1) coupled by an elastic power transmission. The elastic compliance resides in the rotor module that includes the membrane-embedded FO c-ring. Proton transport by FO is firmly coupled to the rotation of the c-ring relative to other FO subunits (ab2). It drives ATP synthesis. We used a computational method to investigate the contribution of the c-ring to the total elastic compliance. We performed principal component analysis of conformational ensembles built using distance constraints from the bovine mitochondrial c-ring x-ray structure. Angular rotary twist, the dominant ring motion, was estimated to show that the c-ring accounted in part for the measured compliance. Ring rotation was entrained to rotation of the external helix within each hairpin-shaped c-subunit in the ring. Ensembles of monomer and dimers extracted from complete c-rings showed that the coupling between collective ring and the individual subunit motions was independent of the size of the c-ring, which varies between organisms. Molecular determinants were identified by covariance analysis of residue coevolution and structural-alphabet-based local dynamics correlations. The residue coevolution gave a readout of subunit architecture. The dynamic couplings revealed that the hinge for both ring and subunit helix rotations was constructed from the proton-binding site and the adjacent glycine motif (IB-GGGG) in the midmembrane plane. IB-GGGG motifs were linked by long-range couplings across the ring, while intrasubunit couplings connected the motif to the conserved cytoplasmic loop and adjacent segments. The correlation with principal collective motions shows that the couplings underlie both ring rotary and bending motions. Noncontact couplings between IB-GGGG motifs matched the coevolution signal as well as contact couplings. The residue coevolution reflects the physiological importance of the dynamics that may link proton transfer to ring compliance.

Dataset Information

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

Publications

Direct observation of stepped proteolipid ring rotation in E. coli F₀F₁-ATP synthase.

Similar Datasets

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