INVITRO PHOSPHORYLATION OF 3-HYDROXY-3-METHYLGLUTARYL COENZYME A REDUCTASE - ANALYSIS OF P-32-LABELED, INACTIVATED ENZYME

Rat liver microsomal 3-hydroxy-3-methylglutaryl-CoA reductase was inactivated with Mg2+ and [γ-32P]ATP, then solubilized and purified to homogeneity. The 32P radioactivity was precipitated by antibody to homogeneous rat liver reductase and comigrated with nonprecipitated, homogeneous reductase on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Under nondenaturing conditions, 32P radioactivity comigrated with reductase protein and activity on polyacrylamide gels. These results provide direct support for the concept that the enzyme is covalently phosphorylated during the in vitro incubation of microsomes with Mg2+ and ATP. © 1979.