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Predicate | Object |
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rdf:type | |
lifeskim:mentions | |
pubmed:issue |
8
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pubmed:dateCreated |
1982-8-7
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pubmed:abstractText |
Limited alpha-chymotryptic digestion of Ca2+-, calmodulin-dependent myosin light chain kinase partially purified from smooth muscle (turkey gizzard) yielded a Ca2+-independent form of the enzyme. Digestion to yield the Ca2+-independent kinase required the enzyme complexed with Ca2+-calmodulin; when digestion was performed on the apoenzyme, i.e., in the absence of Ca2+, the dependence of kinase activity on Ca2+ was retained. The Ca2+-independent kinase was purified by ion-exchange chromatography and shown to have an apparent molecular weight of approximately 80000. The specific activity of the freshly prepared enzyme was 6.5 +/- 0.2 mumol of Pi incorporated min-1 mg-1 in the presence of Ca2+ and 8.3 +/- 0.3 mumol min-1 mg-1 in the absence of Ca2+, using the isolated light chains of gizzard myosin as the substrate. The Ca2+-independent enzyme also phosphorylated the 20000-dalton light chains of purified myosin and crude actomyosin from turkey gizzard. The Km of the Ca2+-independent kinase for Mg2+-ATP (54 muM) was not significantly different from that of the native, CA2+-dependent enzyme (68 muM). These observations indicate maintenance of the integrity of the active site after digestion with alpha-chymotrypsin. It is suggested that the loss of Ca2+ sensitivity of the kinase after limited proteolysis is due to loss of the calmodulin-binding site from the 80000-dalton fragment. The two sites of phosphorylation by the cyclic AMP dependent protein kinase were also removed by the chymotryptic hydrolysis.
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pubmed:grant | |
pubmed:language |
eng
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pubmed:journal | |
pubmed:citationSubset |
IM
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pubmed:chemical |
http://linkedlifedata.com/resource/pubmed/chemical/Calcium,
http://linkedlifedata.com/resource/pubmed/chemical/Calmodulin,
http://linkedlifedata.com/resource/pubmed/chemical/Chymotrypsin,
http://linkedlifedata.com/resource/pubmed/chemical/Myosin-Light-Chain Kinase,
http://linkedlifedata.com/resource/pubmed/chemical/Protein Kinases
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pubmed:status |
MEDLINE
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pubmed:month |
Apr
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pubmed:issn |
0006-2960
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pubmed:author | |
pubmed:issnType |
Print
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pubmed:day |
13
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pubmed:volume |
21
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pubmed:owner |
NLM
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pubmed:authorsComplete |
Y
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pubmed:pagination |
1919-25
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pubmed:dateRevised |
2009-11-19
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pubmed:meshHeading |
pubmed-meshheading:6896283-Animals,
pubmed-meshheading:6896283-Calcium,
pubmed-meshheading:6896283-Calmodulin,
pubmed-meshheading:6896283-Chromatography, Affinity,
pubmed-meshheading:6896283-Chromatography, Ion Exchange,
pubmed-meshheading:6896283-Chymotrypsin,
pubmed-meshheading:6896283-Gizzard,
pubmed-meshheading:6896283-Molecular Weight,
pubmed-meshheading:6896283-Muscle, Smooth,
pubmed-meshheading:6896283-Myosin-Light-Chain Kinase,
pubmed-meshheading:6896283-Osmolar Concentration,
pubmed-meshheading:6896283-Protein Kinases,
pubmed-meshheading:6896283-Turkeys
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pubmed:year |
1982
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pubmed:articleTitle |
Calcium-independent myosin light chain kinase of smooth muscle. Preparation by limited chymotryptic digestion of the calcium ion dependent enzyme, purification, and characterization.
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pubmed:publicationType |
Journal Article,
Research Support, U.S. Gov't, P.H.S.
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