Multiple mRNA species code for the catalytic subunit of the cAMP‐dependent protein kinase from LLC‐PK1 cells

Abstract
We present evidence for the existence of two forms of the catalytic (C) subunit of the cAMP-dependent protein kinase. A .lambda.CAT3, apparently encoded two forms of C subunit designated C.alpha. and C.beta., respectively. The nucleotide sequence of the C.alpha. and C.beta. cDNAs revealed differences in the coding region and particularly in the 3'' untranslated region. However, the deduced amino acid sequences of C.alpha. and C.beta. subunits were 96% homologous to the sequences so far determined. Specific probes from the 3'' coding region of the two cDNA species were used to investigate C subunit mRNA expression in LLC-PK1 cells. Northern analysis showed a major mRNA species of 2.8 kb with the C.alpha. probe while the C.beta. probe detected two mRNA species of 5.0 kg and 3.8 kg. These data were supported by genomic blot analysis which showed distinct hybridization patterns with either the C.alpha. or C.beta. probes. All the available evidence suggests that at least two distinct genes encode the C subunit which are expressed in LLC-PK1 cells.