{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,9,19]],"date-time":"2025-09-19T11:00:02Z","timestamp":1758279602605},"reference-count":0,"publisher":"Portland Press Ltd.","issue":"3","content-domain":{"domain":["portlandpress.com"],"crossmark-restriction":true},"short-container-title":[],"published-print":{"date-parts":[[1988,11,1]]},"abstract":"<jats:p>Caldesmon, an actin- and calmodulin-binding protein of smooth muscle, is a protein serine\/threonine kinase capable of Ca2+\/calmodulin-dependent autophosphorylation [Scott-Woo &amp; Walsh (1988) Biochem. J. 252, 463-472]. Phosphorylation nullifies the inhibitory effect of caldesmon on the actin-activated Mg2+-ATPase activity of smooth-muscle myosin [Ngai &amp; Walsh (1987) Biochem. J. 244, 417-425]. We have characterized the kinase activity of caldesmon of chicken gizzard smooth muscle. Autophosphorylation requires Ca2+\/calmodulin, but is unaffected by other second messengers (Ca2+\/phospholipid\/diacylglycerol, cyclic AMP or cyclic GMP), and is inhibited by the calmodulin antagonists chlorpromazine and compound 48\/80, with 50% inhibition at 39.8 microM and 12.0 ng\/ml respectively. Half-maximal activation of autophosphorylation occurs at 60-80 nM-Ca2+ and 0.14 microM-calmodulin, and maximal activity at 0.14-0.18 microM-Ca2+ and 1 microM-calmodulin; activation is gradually lost at higher Ca2+ and calmodulin concentrations. Autophosphorylation is pH-dependent, with maximal activity over the range pH 7-9, and requires free Mg2+ in addition to the MgATP2- substrate. The Km for ATP is 15.6 +\/- 4.1 microM (mean +\/- S.D., n = 4), and kinase activity is inhibited by increasing ionic strength [half-maximal inhibition at I = 0.094 +\/- 0.009 M (mean +\/- S.D., n = 4)]. Autophosphorylation does not affect the rate of hydrolysis of caldesmon (free or bound to calmodulin) by alpha-chymotrypsin. However, a slight difference in peptides generated from phospho- and dephospho-forms of caldesmon is observed. The binding of phospho- or dephospho-caldesmon to F-actin protects the protein against chymotryptic digestion, but does not alter the pattern of peptide generation. Characterization of proteolytic fragments of caldesmon generated by alpha-chymotrypsin and Staphylococcus aureus V8 protease enables localization of the phosphorylation sites and the kinase active site within the caldesmon molecule.<\/jats:p>","DOI":"10.1042\/bj2550817","type":"journal-article","created":{"date-parts":[[2015,8,10]],"date-time":"2015-08-10T21:12:33Z","timestamp":1439241153000},"page":"817-824","update-policy":"http:\/\/dx.doi.org\/10.1042\/crossmark_policy","source":"Crossref","is-referenced-by-count":8,"title":["Characterization of the autophosphorylation of chicken gizzard caldesmon"],"prefix":"10.1042","volume":"255","author":[{"given":"G C","family":"Scott-Woo","sequence":"first","affiliation":[{"name":"Department of Medical Biochemistry, Faculty of Medicine, University of Calgary, Calgary, Alberta, Canada T2N 4N I"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"M P","family":"Walsh","sequence":"additional","affiliation":[{"name":"Department of Medical Biochemistry, Faculty of Medicine, University of Calgary, Calgary, Alberta, Canada T2N 4N I"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"288","container-title":["Biochemical Journal"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/portlandpress.com\/biochemj\/article-pdf\/255\/3\/817\/594255\/bj2550817.pdf","content-type":"application\/pdf","content-version":"vor","intended-application":"syndication"},{"URL":"https:\/\/portlandpress.com\/biochemj\/article-pdf\/255\/3\/817\/594255\/bj2550817.pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2021,11,25]],"date-time":"2021-11-25T18:06:45Z","timestamp":1637863605000},"score":1,"resource":{"primary":{"URL":"https:\/\/portlandpress.com\/biochemj\/article\/255\/3\/817\/24330\/Characterization-of-the-autophosphorylation-of"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[1988,11,1]]},"references-count":0,"journal-issue":{"issue":"3","published-print":{"date-parts":[[1988,11,1]]}},"URL":"https:\/\/doi.org\/10.1042\/bj2550817","relation":{},"ISSN":["0264-6021","1470-8728"],"issn-type":[{"value":"0264-6021","type":"print"},{"value":"1470-8728","type":"electronic"}],"subject":[],"published":{"date-parts":[[1988,11,1]]}}}