期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2015
卷号：112
期号：12
页码：3716-3721
DOI：10.1073/pnas.1502299112
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：SignificanceIn the heart, phospholamban regulates Ca2+-ATPase function, controlling cardiac output. A single deletion (R14del) in the phospholamban recognition sequence kinase A is linked to the progression of familial dilated cardiomyopathy, a leading cause of death worldwide. Here, we provide the molecular mechanism for the sluggish phosphorylation of R14del by protein kinase A. We found that the R14 deletion affects the organization of the active site, which remains partially open and quite dynamic, preventing the formation of catalytically committed complex. We conclude that well-tuned structural and dynamic interplay between kinase and substrate is crucial for efficient phosphorylation. These results provide new structural basis to understand for the reduced phosphorylation levels of the R14del phospholamban and impaired Ca2+ transport in heart muscle. The dynamic interplay between kinases and substrates is crucial for the formation of catalytically committed complexes that enable phosphoryl transfer. However, a clear understanding on how substrates modulate kinase structural dynamics to control catalytic efficiency is still missing. Here, we used solution NMR spectroscopy to study the conformational dynamics of two complexes of the catalytic subunit of the cAMP-dependent protein kinase A with WT and R14 deletion phospholamban, a lethal human mutant linked to familial dilated cardiomyopathy. Phospholamban is a central regulator of heart muscle contractility, and its phosphorylation by protein kinase A constitutes a primary response to {beta}-adrenergic stimulation. We found that the single deletion of arginine in phospholamban's recognition sequence for the kinase reduces its binding affinity and dramatically reduces phosphorylation kinetics. Structurally, the mutant prevents the enzyme from adopting conformations and motions committed for catalysis, with concomitant reduction in catalytic efficiency. Overall, these results underscore the importance of a well-tuned structural and dynamic interplay between the kinase and its substrates to achieve physiological phosphorylation levels for proper Ca2+ signaling and normal cardiac function.
