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Stabilization of Fo/Vo/Ao by a radial electric field

View Article: PubMed Central - PubMed

ABSTRACT

The membrane domain of rotary ATPases (Fo/Vo/Ao) contains a membrane-embedded rotor ring which rotates against an adjacent cation channel-forming subunit during catalysis. The mechanism that allows stabilization of the highly mobile and yet tightly connected domains during operation while not impeding rotation is unknown. Remarkably, all known ATPase rotor rings are filled by lipids. In the crystal structure of the rotor ring of a V-ATPase from Enterococcus hirae the ring filling lipids form a proper membrane that is lower with respect to the embedding membrane surrounding both subunits. I propose first, that a vertical shift between lumenal lipids and embedding outside membrane is a general feature of rotor rings and second that it leads to a radial potential fall-off between rotor ring and cation channel, creating attractive forces that impact rotor-stator interaction in Fo/Vo/Ao during rotation.

No MeSH data available.


(A) Cross-section through the K-ring horizontal to the membrane plane at the height of the sodium binding sites. (B) Close-up of the same cross-section. The proximity of the bound sodium to structural water of the ring inside is indicated by broken lines and the horizontal line-up of charges by the colored spheres of a lipid head group phosphate (yellow), the terminal nitrogen of lysine 32 (green) and a structural water (blue).
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f3-7_99: (A) Cross-section through the K-ring horizontal to the membrane plane at the height of the sodium binding sites. (B) Close-up of the same cross-section. The proximity of the bound sodium to structural water of the ring inside is indicated by broken lines and the horizontal line-up of charges by the colored spheres of a lipid head group phosphate (yellow), the terminal nitrogen of lysine 32 (green) and a structural water (blue).

Mentions: A cross-section of the K-ring from Enterococcus hirae shows the outside-bound sodium cation to be horizontally in line with alternating charges of a negatively charged lipid head group phosphate, the terminal positive nitrogen of lysine 32 and the partially negative charged water oxygen (Fig. 3A, B). This arrangement could strongly influence the local dielectric environment. The distance between sodium cation and the closest structural water on the inside of the rotor ring is less than 12 Ångstrom (Fig. 3B). This is much shorter than the phosphate-to-phosphate distance of more than 33 Ångstrom observed between lipid molecules in the two leaflets of membranes surrounding bacteriorhodopsin (pdb 2AT9) or aquaporin0 (pdb 2B6O)37 and the inner membrane of the K-ring (pdb 2BL2). It is also considerably shorter than the distance between neighboring sodium ions in the K-ring of 20 Ångstrom or the effective distance of ~18 Ångstrom between proton acceptor/donor sites proposed for Fo-a23.


Stabilization of Fo/Vo/Ao by a radial electric field
(A) Cross-section through the K-ring horizontal to the membrane plane at the height of the sodium binding sites. (B) Close-up of the same cross-section. The proximity of the bound sodium to structural water of the ring inside is indicated by broken lines and the horizontal line-up of charges by the colored spheres of a lipid head group phosphate (yellow), the terminal nitrogen of lysine 32 (green) and a structural water (blue).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC5036770&req=5

f3-7_99: (A) Cross-section through the K-ring horizontal to the membrane plane at the height of the sodium binding sites. (B) Close-up of the same cross-section. The proximity of the bound sodium to structural water of the ring inside is indicated by broken lines and the horizontal line-up of charges by the colored spheres of a lipid head group phosphate (yellow), the terminal nitrogen of lysine 32 (green) and a structural water (blue).
Mentions: A cross-section of the K-ring from Enterococcus hirae shows the outside-bound sodium cation to be horizontally in line with alternating charges of a negatively charged lipid head group phosphate, the terminal positive nitrogen of lysine 32 and the partially negative charged water oxygen (Fig. 3A, B). This arrangement could strongly influence the local dielectric environment. The distance between sodium cation and the closest structural water on the inside of the rotor ring is less than 12 Ångstrom (Fig. 3B). This is much shorter than the phosphate-to-phosphate distance of more than 33 Ångstrom observed between lipid molecules in the two leaflets of membranes surrounding bacteriorhodopsin (pdb 2AT9) or aquaporin0 (pdb 2B6O)37 and the inner membrane of the K-ring (pdb 2BL2). It is also considerably shorter than the distance between neighboring sodium ions in the K-ring of 20 Ångstrom or the effective distance of ~18 Ångstrom between proton acceptor/donor sites proposed for Fo-a23.

View Article: PubMed Central - PubMed

ABSTRACT

The membrane domain of rotary ATPases (Fo/Vo/Ao) contains a membrane-embedded rotor ring which rotates against an adjacent cation channel-forming subunit during catalysis. The mechanism that allows stabilization of the highly mobile and yet tightly connected domains during operation while not impeding rotation is unknown. Remarkably, all known ATPase rotor rings are filled by lipids. In the crystal structure of the rotor ring of a V-ATPase from Enterococcus hirae the ring filling lipids form a proper membrane that is lower with respect to the embedding membrane surrounding both subunits. I propose first, that a vertical shift between lumenal lipids and embedding outside membrane is a general feature of rotor rings and second that it leads to a radial potential fall-off between rotor ring and cation channel, creating attractive forces that impact rotor-stator interaction in Fo/Vo/Ao during rotation.

No MeSH data available.