Effects of potassium on vanadate inhibition of sarcoplasmic reticulum Ca2+-ATPase from dog cardiac and rabbit skeletal muscle

Vanadate inhibition of the Ca2+‐dependent conformational change of the sarcoplasmic reticulum Ca2+‐ATPase

“…A 50% inhibition of the steady state rate of the Ca2*-ATPase was obtained at -10 PM vanadate or above which is much higher than the affinity for the E state measured here [7,8]. This weak inhibitory effect on the ATPase activity, confirmed by us (not shown), indicates that most of the steady state intermediates formed are less susceptible to vanadate than the calcium free E conformation, being either the E-Mg-P or the Et' .…”

“…Binding to the phosphorylation site is facilitated by K+ and Mg2+ and locks the enzyme in the Ez state . Vanadate inhibition of Ca2+-ATPase activity of sarcoplasmic reticulum has been reported in [7,8], the apparent affinity for the inhibitor being however much lower than for the __ (Na',K+)ATPase.…”

Effects of soldium vanadate on the smooth muscle of the guinea-pig vas deferens.

“…In the latter case, the inhibition of Ca-ATPase of membranous systems (Wang et al, 1979;Wierichs et al, 1980;Caroni & Carafoli, 1981a;Caroni & Carafoli, 1981b) which leads to net release of Ca may be the cause of an increase in tension.…”

“…In certain heart muscles, inhibitions of Na, K-ATPase is thought to be main cause regarding positive inotropic effects of venadate (Hackbarth et al, 1978;Grupp et al, 1979;Bochard et al, 1979;Myers & Boerth, 1980) similar to the action of ouabain, while, in other heart muscles, vanadate shows a negative inotropic effect (Akeraet al, 1979;Grupp et al, 1979;Solaro et al, 1980). Vanadate has also an inhibitory action on CaATPase activity and Ca transport of sarcolmma and sarcoplasmic reticulum of heart muscle (Wang et al, 1979;Solaro et al, 1980;Wierichs et al, 1980;Caroni & Carafori, 1981a;Caroni & Carafori, 1981b;Morcos, 1982) and sarcoplasmic reticulum of skeletal muscle (O'Neal et al, 1979;Wang et al, 1979). The effects on Ca-ATPase may also provide changes in the contraction of these muscles.…”

Mg(2+),ATP-dependent plasma membrane calcium pump of smooth muscle cells. ІІ. Regulation of activity

“…Класичним неспецифічним інгібітором катіонтранспортувальних АТРаз Р-типу є ор-тованадат [26,39,40]. Ця сполука гальмує Ca 2+ -помпи СР та ПМ, але чутливість цих си-стем до нього відрізняється [8,26,27]. При-пускають, що ванадат (п'ятивалентний сте-ричний аналог фосфату) пригнічує активність АТРази, зв'язуючись з аспарагіновою кисло-тою, яка бере участь в утворенні проміжного фосфоризованого продукту Са…”