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)

Kinesin is a microtubule-activated, mechanochemical ATPase capable of moving particles along microtubules and making microtubules glide along a solid substrate. In this study we used limited proteolysis to study the structure of bovine brain kinesin, a heterotetramer composed of two heavy (120-kDa) and two light (62-kDa) chains. alpha-chymotrypsin, trypsin, and subtilisin all produced a protease-resistant 45-kDa fragment from the kinesin heavy chain. As isolated by gel-filtration chromatography, this fragment contains both the microtubule-binding site and the ATP catalytic site of the molecule. Proteolytic cleavage stimulated microtubule-dependent Mg2+-ATPase activity 4- to 5-fold up to 75-120 mumol ATP/min/mg. Cleavage also increased the affinity of the fragment for microtubules at least 10-fold. Since the purified fragment does not support the gliding of flagellar axonemes, we propose that cleavage of the heavy chain uncouples ATPase activity from its translocator activity, which may require other parts of the molecule.
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PMID:Isolation of a 45-kDa fragment from the kinesin heavy chain with enhanced ATPase and microtubule-binding activities. 252 Dec 21

Previous work (Maruta, H., Gadasi, H., Collins, J. H., and Korn, E. D. (1978) J. Biol. Chem. 253, 6292-6300) had shown that phosphorylation of the heavy chain of Acanthamoeba myosin IA is required for actin activation of its Mg2+-ATPase activity and that, like the phosphorylation site, the catalytic site and the actin binding site are also on the heavy chain. We now show that limited digestion of phosphorylated myosin IA by subtilisin allows separation of the catalytically active peptide fragment from the phosphorylated peptide without any significant loss of actin-activated Mg2+-ATPase activity. A proteolytic fragment with full actin-activated Mg2+-ATPase activity has also been isolated from subtilisin digests of nonphosphorylated myosin IA, which, before proteolysis, did not have actin-activated Mg2+-ATPase activity. The simplest interpretation of these data is that, in its nonphosphorylated state, the phosphorylation site of Acanthamoeba myosin IA inhibits the catalytic site and that this inhibition can be reversed either by phosphorylation of the site or by proteolytically separating it from the catalytic site. Alternatively, phosphorylation and proteolysis may, by unrelated mechanisms, induce similar conformational changes in the myosin heavy chain that lead to activation of its actomyosin ATPase activity.
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PMID:Proteolytic separation of the actin-activatable ATPase site from the phosphorylation site on the heavy chain of Acanthamoeba myosin IA. 610 57