A cDNA encoding the skeletal muscle phosphorylase kinase catalytic subunit gamma has been isolated and sequenced. It contains 57 nucleotides of 5' nontranslated sequence, the entire coding sequence, and 1004 nucleotides of 3' nontranslated sequence. Probes derived from this gamma-cDNA were used to investigate the expression of gamma-messages in liver, heart, and skeletal muscle tissues. The results demonstrate that the gamma-mRNAs expressed in heart tissue are homologous to the skeletal muscle gamma-mRNAs. However, in liver tissue, no homologous gamma-mRNAs were detected. The implications of these results for understanding gamma-isoform expression and the possibility of a liver-specific gamma-gene are discussed.