Sodium or lithium ion-binding-induced structural changes in the K-ring of V-ATPase from Enterococcus hirae revealed by ATR-FTIR spectroscopy.

Yuji Furutani, Takeshi Murata, Hideki Kandori

Department of Frontier Materials, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan.

Journal of the American Chemical Society 2011 Mar 9

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V-ATPase from Enterococcus hirae forms a large supramolecular protein complex (total molecular weight ∼700,000) and physiologically transports Na(+) and Li(+) across a hydrophobic lipid bilayer. Stabilization of these cations in the binding site has been discussed on the basis of X-ray crystal structures of a membrane-embedded domain, the K-ring (Na(+)- and Li(+)-bound forms). Here, sodium or lithium ion-binding-induced difference IR spectra of the intact V-ATPase have for the first time been measured at physiological temperature under a sufficient amount of hydration. The results suggest that sodium or lithium ion binding induces the deprotonation of Glu139, a hydrogen-bonding change in the tyrosine residue, and a small conformational change in the K-ring. These structural changes, especially the deprotonation of Glu139, are considered to be important for reducing energetic barriers to the transport of cations through the membrane.

Citation

Yuji Furutani, Takeshi Murata, Hideki Kandori. Sodium or lithium ion-binding-induced structural changes in the K-ring of V-ATPase from Enterococcus hirae revealed by ATR-FTIR spectroscopy. Journal of the American Chemical Society. 2011 Mar 9;133(9):2860-3