Intersubunit capture of regulatory segments is a component of cooperative CaMKII activation.
The dodecameric holoenzyme of calcium-calmodulin-dependent protein kinase II (CaMKII) responds to high-frequency Ca(2+) pulses to become Ca(2+) independent. A simple coincidence-detector model for Ca(2+)-frequency dependency assumes noncooperative activation of kinase domains. We show that activation of CaMKII by Ca(2+)-calmodulin is cooperative, with a Hill coefficient of approximately 3.0, implying sequential kinase-domain activation beyond dimeric units. We present data for a model in which cooperative activation includes the intersubunit 'capture' of regulatory segments. Such a capture interaction is seen in a crystal structure that shows extensive contacts between the regulatory segment of one kinase and the catalytic domain of another. These interactions are mimicked by a natural inhibitor of CaMKII. Our results show that a simple coincidence-detection model cannot be operative and point to the importance of kinetic dissection of the frequency-response mechanism in future experiments.
Department of Molecular and Cell Biology, University of California, Berkeley, California, USA.
Luke H
LH
Chao
Patricia
P
Pellicena
Sebastian
S
Deindl
Lauren A
LA
Barclay
Howard
H
Schulman
John
J
Kuriyan
D000818:Animals; D001665:Binding Sites; D017173:Caenorhabditis elegans / Q000201:enzymology; D029742:Caenorhabditis elegans Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D002147:Calmodulin / Q000378:metabolism; D018360:Crystallography, X-Ray; D006801:Humans; D008954:Models, Biological; D010766:Phosphorylation; D011485:Protein Binding / Q000235:genetics / Q000502:physiology; D017433:Protein Structure, Secondary
D029742:Caenorhabditis elegans Proteins; D002147:Calmodulin; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D002118:Calcium