Vanadate

About: Vanadate is a research topic. Over the lifetime, 4497 publications have been published within this topic receiving 120109 citations. The topic is also known as: vanadate.

Characterization of a Proton-Translocating ATPase in Microsomal Vesicles from Corn Roots

Abstract: Sealed microsomal vesicles were prepared from corn (Zea mays, Crow Single Cross Hybrid WF9-Mo17) roots by centrifugation of a 10,000 to 80,000g microsomal fraction onto a 10% dextran T-70 cushion. The Mg(2+)-ATPase activity of the sealed vesicles was stimulated by Cl(-) and NH(4) (+) and by ionophores and protonophores such as 2 micromolar gramicidin or 10 micromolar carbonyl cyanide p-trifluoromethoxyphenyl hydrazone (FCCP). The ionophore-stimulated ATPase activity had a broad pH optimum with a maximum at pH 6.5. The ATPase was inhibited by NO(3) (-), was insensitive to K(+), and was not inhibited by 100 micromolar vanadate or by 1 millimolar azide.Quenching of quinacrine fluorescence was used to measure ATP-dependent acidification of the intravesicular volume. Quenching required Mg(2+), was stimulated by Cl(-), inhibited by NO(3) (-), was insensitive to monovalent cations, was unaffected by 200 micromolar vanadate, and was abolished by 2 micromolar gramicidin or 10 micromolar FCCP. Activity was highly specific for ATP. The ionophore-stimulated ATPase and ATP-dependent fluorescence quench both required a divalent cation (Mg(2+) >/= Mn(2+) > Co(2+)) and were inhibited by high concentrations of Ca(2+). The similarity of the ionophore-stimulated ATPase and quinacrine quench and the responses of the two to ions suggest that both represent the activity of the same ATP-dependent proton pump. The characteristics of the proton-translocating ATPase differed from those of the mitochondrial F(1)F(0)-ATPase and from those of the K(+)-stimulated ATPase of corn root plasma membranes, and resembled those of the tonoplast ATPase.

Partial characterization of a phosphorylated intermediate associated with the plasma membrane ATPase of corn roots.

Abstract: The phosphorylated protein associated with a deoxycholate-extracted plasma membrane fraction from corn (Zea mays L. var WF9 × Mol7) roots was characterized in order to correlate its properties with those of plasma membrane ATPase. Its phosphorylation, like that of plasma membrane ATPase, was dependent on Mg2+, substrate specific for ATP, insensitive to azide, oligomycin, or molybdate, and sensitive to N,N′-dicyclohexylcarbodiimide, diethylstilbestrol, or vanadate. Monovalent cations affected the phosphorylation of the protein in a manner consistent with their stimulatory effects on ATPase. For K+, this was shown to occur through an increase in the turnover of the phosphoenzyme. Analysis of the phosphorylated protein by NaDodSO4/polyacrylamide gel electrophoresis revealed the presence of a single labeled polypeptide with a molecular weight of about 100,000. Phosphorylation of this polypeptide was dependent on Mg2+, sensitive to K+, and inhibited by vanadate. It is concluded that this polypeptide represents the catalytic subunit of the plasma membrane ATPase. These results are discussed in terms of a model for the coupling of metabolic energy to H+ and K+ transport in higher plants.

Vanadate and the absence of myofibroblasts in wound contraction.

Abstract: Hypothesis Fibroblasts, not myofibroblasts, are responsible for wound contraction. Only myofibroblasts express a smooth muscle actin for which vanadate blocks its expression. Wound contraction in vanadate-treated rats will proceed normally in the absence of myofibroblasts. Design Laboratory study using rats. Methods Wound healing in rats receiving vanadate parenterally, an inhibitor of tyrosine phosphate phosphatases, was investigated. For 21 days, treated rats received drinking water containing vanadate, 0.2 mg/mL, in isotonic sodium chloride solution, and the control rats received isotonic sodium chloride solution alone. On day 7, 4 square, full-excision wounds were made dorsally and measured, then 2 polyvinyl alcohol sponges were placed ventrally in subcutaneous pockets. Results After 2 weeks, the wound area in the rats receiving vanadate measured 7.1±1.8 U (mean±SD), and the wound area in the control rats measured 7.2±2.2 U. The control rats' granulation tissue (GT) had myofibroblasts, or α-smooth muscle (α-SM) actin-positive fibroblasts, whereas the vanadate-treated group's fibroblasts were devoid of α-SM actin. By Western blot analysis, GT homogenates in the vanadate-treated group contained less α-SM actin. By electron microscopy, control rats' GT showed classic myofibroblast populations, and the collagen fiber bundles were randomly organized. In contrast, the wounds in the vanadate-treated group showed unencumbered fibroblast populations and neatly ordered, parallel collagen fiber bundles. By polarized light microscopy, the GT of the vanadate-treated group displayed orderly collagen fiber bundles. Conclusions The differentiation of fibroblasts into myofibroblasts requires the dephosphorylation of selected tyrosine phosphate residues. In the absence of myofibroblasts, the rate of rat wound contraction is normal, and collagen fiber bundles have a more orderly arrangement. Myofibroblasts are not required for wound contraction.