Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.6.3.1 (Mg2+-ATPase)
 1,484 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Actomyosin Mg2+-ATPase activity was stimulated by a brain microtubule-associated protein (MAP) fraction. The stimulating activity of the MAP fraction was abolished by boiling and trypsin treatment, suggesting the presence of a protein factor. The factor stimulated actomyosin Mg2+-ATPase activity stoichiometrically by about four times in the optimum conditions (50--75 mM KCl, pH 6.6). The stimulating factor was coprecipitable with actomyosin and was found to be a pair of high-molecular-weight polypeptides (mol wts, 240,000 and 235,000). The polypeptides were not associated with microtubules or myosin, but with fibrous actin. In column chromatographies used for purifying the stimulating factor, the amount of polypeptides coincided with the stimulating activity. Increases in both specific activity and the amount of the paired polypeptides were nearly parallel in the process of the purification. A purified fraction (65% pure with respect to the paired polypeptides) showed a 56-fold increase of the specific stimulating activity as compared with the initial brain supernatant. The two peptides were similar but not identical with filamin and spectrin in terms of electrophoretic mobility. Hence, the pair of polypeptides was identified as an actin-binding protein newly found in brain.
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PMID:Stimulation of actomyosin Mg2+-ATPase activity by a brain microtubule-associated protein fraction. High-molecular-weight actin-binding protein is the stimulating factor. 612 91

Taxol, an antimitotic agent that induces microtubule assembly, stimulated tubulin-dependent Mg2+-ATPase activity of microtubule-associated proteins (MAPs). A concentration-dependent increase in the rate of ATP hydrolysis was observed. Taxol acted through its binding to the tubulin molecule on MAP ATPase, and maximal stimulation, which was found at approximately equal concentrations of taxol and tubulin, reached about 140% of the original level in the absence of taxol. Taxol enhanced ATP hydrolysis by a mixture of MAPs and tubulin, and this continued at a steady linear rate even when the polymerization had approached a plateau. In the presence of taxol, a large portion of ATPase activity and protein was recovered in the pellet after centrifugation at 70,000 g for 60 min at 25 degrees C. Both colchicine and podophyllotoxin inhibited taxol-stimulated ATPase activity via the same mechanism by which they inhibited taxol-induced microtubule polymerization. The stimulation by taxol was not found in the presence of Ca2+ alone but required Mg2+. We conclude that tubulin effectively stimulates Mg2+-ATPase activity of MAPs under conditions that induce tubulin polymerization.
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PMID:Stimulation of tubulin-dependent ATPase activity in microtubule proteins from porcine brain by taxol. 613 58