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Abstract
Ca2+transport has been measured across plasma membrane vesicles isolated from cells of Ustilago maydis. This transport was found to be ATP- (or to a lesser extent GTP) and Mg2+-dependent. Inconsistent release of Ca2+from intact vesicles was obtained using the calcium ionophore A23187. However, Ca2+was released by Triton X-100 in a concentration-dependent manner. Transport was inhibited by vanadate (>50%) and erythrosin B (about 50%), I 50being about 10 μM for both inhibitors. In the presence of the protonophores CCCP or gramicidin, partial inhibition of Ca2+transport (about 20%) was observed, but the Ca2+-channel blockers, nifedipine, diltiazem and verapamil had no effect, although the latter inhibited proton transport. The results indicate that Ca2+transport in U. maydisis regulated by a P-type ATPase with similar properties to that found in higher plants.
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