86Rb+ Uptake

Fig. 8. Proton activation of KcsA. (A) Time course of 86Rb+ uptake depends on ex-travesicular pH. Open circles, uptake at pH 7.0 (left) or 3.5 (right). Filled circles, uptake in the presence of 10 mM BaClg in both sides of the membrane. (B) pH effect on singlechannel properties of KcsA in planar lipid bilayers. Top Consecutive single-channel traces obtained at pH 4.0, 4.5, 5.0 and 6.0 for a multichannel asolectin bilayer. Bottom panels All-point histogram corresponding to each set of single-channel records.

The Na-K ATPase, in the plasma membrane of mammalian cells, is inhibited when ouabain binds to the a subunit that is phosphorylated during catalysis.21 372 Unlike HGPRT" and TK"/", the ouabain-resistant phenotype (assigned to chromosome 3 in the mouse)218 is dominant, stable, and characterized by a reduced uptake of 86Rb and 1 2K in the presence of ouabain and by reduced binding of ouabain to the plasma membrane.21 Ouabain resistance can be induced... 

In studies performed by Endre et al., rat kidneys were perfused with Rb+-containing Krebs bicarbonate buffer.55,95 A tracer quantity of radioactive 86Rb+ was added to the perfusate in some experiments to evaluate the NMR visibility of the intracellular 87 Rb. The uptake of NMR-detectable Rb+ into the kidney was analysed in terms of the model discussed above. The kinetic parameters obtained from three experiments were V b + kIE = 0.92 0.07 /xmol/ming,... 

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