Characterization of the gene for rat phosphorylase kinase catalytic subunit

Phosphorylase kinase, a key enzyme in glycogen metabolism, has a subunit composition of (alpha beta gamma delta)4, in which the alpha and beta subunits are regulatory, delta is calmodulin, and the gamma subunit is catalytic. As one segment of our studies on the regulation of the expression of phosphorylase kinase subunits, we present in this report the structure of the gene for the catalytic gamma subunit. The gene extends over 16 kilobase pairs (kb) of DNA, and contains eight introns within the coding region plus one 3.3-kb intron upstream in the 5'-untranslated region. Within this first intron, and also upstream of the transcription start site, are sequences homologous to defined regulatory elements, including some found in other muscle-specific genes. The positions of intron splice junctions for this gene have been compared with similar data for other protein kinase genes. A somewhat unexpected finding for the gamma subunit is that two of the splice junctions fall in the midst of highly conserved strings of amino acids, both of which have been nominally defined as functional domains for the protein kinases and appear to make key contributions to substrate binding and phosphotransferase catalysis.