A novel pancreatic β-cell isoform of calcium/calmodulin-dependent protein kinase II (β3isoform) contains a proline-rich tandem repeat in the association domain

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Abstract
There is evidence for a role for calciumlcalmodulin-dependent protein phosphorylation in regulation of insulin secretion but the molecular nature of the kinase(s) responsible is unknown. In this study, the screening of a neonatal rat islet cDNA library resulted in the isolation of a 2 kb clone that was 99% homologous to the β′ isoform of calciumlcalmodulin-dependent protein kinase 11. The predicted 589 amino acid sequence with a caLculated mass of 64,976 Da contained a 24 amino acid deletion in addition to the 15 amino acid deletion that differentiates the β′ from the β isoform, and included an 86 amino acid novel domain consisting of a tandem repeat of proline-rich residues. The expression of this new isoform of calciumlcalmodulin-dependent protein kinase 11 (β 3) was confirmed in β-cell lines and testis by DNA amplification of the sequence encoding the inserted domain by reverse transcriptase-polymerase chain reaction, followed by Southern analysis.