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Journal Article

Molecular architecture of the undecameric rotor of a bacterial Na+-ATP synthase

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Vonck,  J.
Department of Structural Biology, Max Planck Institute of Biophysics, Max Planck Society;

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Meier,  T.
Department of Structural Biology, Max Planck Institute of Biophysics, Max Planck Society;

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Kühlbrandt,  W.
Department of Structural Biology, Max Planck Institute of Biophysics, Max Planck Society;

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Citation

Vonck, J., von Nidda, T. K., Meier, T., Matthey, U., Mills, D. J., Kühlbrandt, W., et al. (2002). Molecular architecture of the undecameric rotor of a bacterial Na+-ATP synthase. Journal of Molecular Biology, 321(2), 307-316.


Cite as: http://hdl.handle.net/11858/00-001M-0000-0024-DC9F-A
Abstract
The sodium ion-translocating F(1)F(0) ATP synthase from the bacterium Ilyobacter tartaricus contains a remarkably stable rotor ring composed of 11 c subunits. The rotor ring was isolated, crystallised in two dimensions and analysed by electron cryo-microscopy. Here, we present an alpha-carbon model of the c-subunit ring. Each monomeric c subunit of 89 amino acid residues folds into a helical hairpin consisting of two membrane-spanning helices and a cytoplasmic loop. The 11 N-terminal helices are closely spaced within an inner ring surrounding a cavity of approximately 17A (1.7 nm). The tight helix packing leaves no space for side-chains and is accounted for by a highly conserved motif of four glycine residues in the inner, N-terminal helix. Each inner helix is connected by a clearly visible loop to an outer C-terminal helix. The outer helix has a kink near the position of the ion-binding site residue Glu65 in the centre of the membrane and another kink near the C terminus. Two helices from the outer ring and one from the inner ring form the ion-binding site in the middle of the membrane and a potential access channel from the binding site to the cytoplasmic surface. Three possible inter-subunit ion-bridges are likely to account for the remarkable temperature stability of I.tartaricus c-rings compared to those of other organisms.