We present evidence for the existence of two forms of the catalytic (C) subunit of the cAMP‐dependent protein kinase. A λgt‐11 cDNA library constructed from poly(A)‐rich RNA from the porcine kidney cell line, LLC‐PK1, was screened using a 1.5‐kb EcoRI fragment from a bovine cDNA for the C subunit. Two independent classes of cDNAs were identified on the basis of partial restriction map and sequence data. These two cDNAs, λCAT4 and λCAT3, apparently encode two forms of C subunit designated Cα and Cβ, respectively. The nucleotide sequence of the Cα and Cβ cDNAs revealed differences in the coding region and particularly in the 3′ untranslated region. However, the deduced amino acid sequences of Cα and Cβ 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 Cα probe while the Cβ probe detected two mRNA species of 5.0 kb and 3.8 kb. These data were supported by genomic blot analysis which showed distinct hybridization patterns with either the Cα or Cβ probes. All the available evidence suggests that at least two distinct genes encode the C subunit which are expressed in LLC‐PK1 cells.
|Number of pages
|European Journal of Biochemistry
|Published - Sep 1987
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