Journal of Biological Chemistry
Volume 278, Issue 40, 3 October 2003, Pages 38593-38600
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Protein Synthesis, Post-Translation Modification, and Degradation
Stoichiometric Phosphorylation of Cardiac Ryanodine Receptor on Serine 2809 by Calmodulin-dependent Kinase II and Protein Kinase A*

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The ryanodine receptor of cardiac muscle performs a central role in excitation-contraction coupling. Phosphorylation of the channel on serine 2809 (in rabbit or the corresponding serine 2808 in man) alters function in vitro, although the impact of this in vivo has not been established. We have produced a pair of antisera to the serine 2809 phosphorylation site to aid description of the incidence and consequence of phosphorylation of this receptor. One of these antisera is specific for the serine 2809 phosphorylated form of the cardiac ryanodine receptor; the other antiserum is specific for the serine 2809 dephosphorylated receptor. These antibodies have been used to demonstrate that both protein kinase A and calmodulin-dependent kinase II are capable of phosphorylating serine 2809 in vitro. Both kinases phosphorylate serine 2809 to full stoichiometry, but this is accompanied by the incorporation of more (radioactive) phosphate into the receptor by calmodulin-dependent kinase II than by protein kinase A. These data suggest that calmodulin-dependent kinase II phosphorylates at least four sites in addition to serine 2809 in vitro.

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*

This work was supported by the British Heart Foundation (PG/99166 and PG/99186). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.