title: Electrokinetic properties of (Na+, K+)-ATPase vesicles as studied by laser Doppler spectroscopy.
abstract: The technique of laser Doppler electrophoresis was applied for the study of the surface charge properties of (NA+, K+)-ATPase containing microsomal vesicles derived from guinea-pig kidney. The influence of pH, the screening and binding of uni- and divalent cations and the binding of ATP show: (1) one net negative charge per protein unit with a pK = 3.9; (2) deviation from the Debye relation between surface potential and ionic strength for univalent cations, with no difference in the effect of Na+ and K+; (3) Mg2+ binds with an association constant of Ka = 1.1. 10(2) M-1 while ATP binds with an apparent Ka = 1.1.10(4) M-1 for 1 mM NaCl, 0.2 mM KCI, 0.1 mM MgCl2, 0.1 mM Tris-HCl2, 0.1 mM Tris-HCl (pH 7.3). The binding is weaker at higher Mg2+ concentrations. There is no ATP binding in the absence of Mg2+. In addition, the average vesicle size derived from the linewidth of the quasielastic light scattering spectrum is 203.7 +/- 15.2 nm. In the presence of ATP a reduction in size is observed.
mesh_terms: D000818:Animals; D006168:Guinea Pigs; D007668:Kidney / Q000201:enzymology*; D007700:Kinetics; D007834:Lasers; D008564:Membrane Potentials; D008854:Microscopy, Electron; D008861:Microsomes / Q000201:enzymology*; D008968:Molecular Conformation; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D013057:Spectrum Analysis / Q000379:methods
chemical_list: D000254:Sodium-Potassium-Exchanging ATPase