Conserved and Variable Regions in the Subunits of Brain Type II Ca^(2+)/Calmodulin-Dependent Protein Kinase

Abstract

Brain type II Ca^(2+)/calmodulin-dependent protein kinase is a holoenzymecomposed of several copies each of three subunits, α (50 kd), β (60 kd), and β' (58 kd), in varying proportions. The deduced amino acid sequences of α (reported here) and β are highly similar but not identical. The major difference between them is the deletion from α of two short segments (residues 316–339 and 354–392 in β). cDNAs that appear to encode β' are identical to b except for the deletion of a segment encoding residues 378–392. Thus, the structural differences among α, β, and β' arise primarily from deletions (or insertions) in a variable region lying immediately carboxyl to the protein kinase and calmodulin-binding domains. The α and β subunits are encoded by distinct genes expressed primarily, if not exclusively, in brain. Rather than being encoded by a third gene, β' may arise by alternative splicing of the β gene transcript.

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