Involved in cardiomyocyte differentiation. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Expressed in the heart and skeletal muscle of adult mice. First detected in the cardiac crescent at 7.5 dpc when the developing heart became visible and remains through to 10.5 dpc. Mice are viable and were born at the expected Mendelian ratio. They however develop spontaneous cardiomyopathy with features of both hypertrophic and dilated forms of cardiomyopathy. Cardiac hypertrophy is characterized by increased thickness of both left and right ventricular walls and by significantly increased heart weight. Some features are also associated with dilated cardiomyopathy. Cardiomyocytes show an altered architecture, characterized by reduced numbers of abnormal intercalated disks. Belongs to the protein kinase superfamily. Alpha-type protein kinase family. ALPK subfamily.