Decavanadate interactions with sarcoplasmic reticulum calcium pump

Although not stable, once formed, decameric vanadate (V10) disintegration is in general slow enough to allow the study of its effects even in the micromolar range. Besides, it may become inaccessible to decomposition due to their specific interaction upon target proteins such as the Ca2+-ATPase from sarcoplasmic reticulum (SR). Characterization of the vanadate solutions and interactions with compounds containing phosphate as well as with the SR Ca2+-ATPase was analysed by 51V NMR spectroscopy. Vanadate is a well known inhibitor of this E1E2 phosphohydrolases and it as been used as a probe in the study of the structure and in the function of the protein. Decameric vanadate species also interact with the SR Ca2+-ATPase but clearly differs from monomeric vanadate by inhibiting sarcoplasmic reticulum calcium translocation at different calcium gradient conditions, coupled or not to ATP hydrolysis. Vanadium(IV) and (V) complexes, some known to have insulinomimetic properties, also inhibit the calcium ATPase activity, although at a lower extend than V10