title: Sodium or lithium ion-binding-induced structural changes in the K-ring of V-ATPase from Enterococcus hirae revealed by ATR-FTIR spectroscopy.
abstract: 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.
authors.affiliation: Department of Frontier Materials, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Furutani
authors.forename: Takeshi
authors.initials: T
authors.lastname: Murata
authors.forename: Hideki
authors.initials: H
authors.lastname: Kandori
mesh_terms: D001665:Binding Sites; D018360:Crystallography, X-Ray; D016983:Enterococcus / Q000201:enzymology*; D007477:Ions / Q000378:metabolism; D008094:Lithium / Q000378:metabolism*; D008958:Models, Molecular; D011485:Protein Binding; D012964:Sodium / Q000378:metabolism*; D017550:Spectroscopy, Fourier Transform Infrared; D025262:Vacuolar Proton-Translocating ATPases / Q000737:chemistry / Q000378:metabolism*
chemical_list: D007477:Ions; D008094:Lithium; D012964:Sodium; D025262:Vacuolar Proton-Translocating ATPases