Characterization of a Ca/sup 2 +/, calmodulin-dependent protein kinase which is able to phosphorylate native and protease cleaved purified hepatic 3-hydroxy-3-methylglutaryl coenzyme A reductase
The authors have extensively purified a low molecular weight Ca/sup 2 +/, calmodulin-dependent protein kinase from rat brain cytosol. This kinase (M/sub r/ 120,000) is able to phosphorylate both native and soluble purified HMG-CoA reductase. The concomitant inactivation and phosphorylation of purified HMG-CoA reductase was completely dependent on Ca/sup 2 +/ and calmodulin. Incubation of phosphorylated /sup 32/P-HMG-CoA reductase was associated with the loss of /sup 32/P-radioactivity and reactivation of inactive enzyme. Maximal phosphorylation of purified HMG-CoA reductase involved the introduction of approximately 0.5 mol phosphate/53,000 enzyme fragment. The apparent Km for purified HMG-CoA reductase was .045 mg/ml. Microsomal native HMG-CoA reductase (M/sub r/ 100,000) was also phosphorylated and inactivated following incubation with calmodulin stimulated kinase, calmodulin, Ca/sup 2 +/ and Mg-ATP; dephosphorylation (reactivation) was catalyzed by the phosphoprotein phosphatase. The isolation and characterization of the M/sub r/ 120,000 calmodulin-binding enzyme complex provides additional insights into the mechanisms of the Ca/sup 2 +/ dependent regulation of HMG-CoA reductase phosphorylation. Based on these data and the authors previous in vitro and in vivo studies, they now propose that HMG-CoA reductase activity is modulated by three separate kinase systems.
- Research Organization:
- National Institutes of Health, Bethesda, MD
- OSTI ID:
- 6832430
- Report Number(s):
- CONF-8606151-; TRN: 87-006994
- Journal Information:
- Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States), Vol. 45:6; Conference: 76. annual meeting of the Federation of American Society for Experimental Biology, Washington, DC, USA, 8 Jun 1986
- Country of Publication:
- United States
- Language:
- English
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550201* - Biochemistry- Tracer Techniques