Effects of cellular protein on CSQ2 kinase activity. a Increasing concentrations, 1, 2, 5, 10, 20, 30 or 50 μg of rat heart cell detergent extract or COS cell homogenate was used to phosphorylate 2 μg of purified native canine CSQ2 (arrowheads). Reaction mixtures were analyzed by SDS-PAGE and [32P]autoradiography. b Radioactive incorporation was determined, and kinase activity is shown on the y-axis. CSQ2 kinase activities are shown in units of mmol Pi incorporation/mol CSQ2/μg protein. c CSQ2 kinase activity was measured in 2, 5 or 20 μg of homogenate, from a detergent extraction of 2, 5 or 20 μg of homogenate, or from a detergent-free extraction of 2, 5 or 20 μg of homogenate derived from cardiomyocytes or COS cells. Gray shading highlights the levels for each preparation that would constitute linearity of CSQ2 kinase activity. d Immunoblot of CK2α or CK2α′ subunits from 50 μg of COS cell homogenate (H), detergent extract (DE), or detergent-free extract (DFE)