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Plant chimeric Ca2+/Calmodulin-dependent protein kinase. Role of the neural visinin-like domain in regulating autophosphorylation and calmodulin affinityChimeric Ca(2+)/calmodulin-dependent protein kinase (CCaMK) is characterized by a serine-threonine kinase domain, an autoinhibitory domain, a calmodulin-binding domain and a neural visinin-like domain with three EF-hands. The neural visinin-like Ca(2+)-binding domain at the C-terminal end of the CaM-binding domain makes CCaMK unique among all the known calmodulin-dependent kinases. Biological functions of the plant visinin-like proteins or visinin-like domains in plant proteins are not well known. Using EF-hand deletions in the visinin-like domain, we found that the visinin-like domain regulated Ca(2+)-stimulated autophosphorylation of CCaMK. To investigate the effects of Ca(2+)-stimulated autophosphorylation on the interaction with calmodulin, the equilibrium binding constants of CCaMK were measured by fluorescence emission anisotropy using dansylated calmodulin. Binding was 8-fold tighter after Ca(2+)-stimulated autophosphorylation. This shift in affinity did not occur in CCaMK deletion mutants lacking Ca(2+)-stimulated autophosphorylation. A variable calmodulin affinity regulated by Ca(2+)-stimulated autophosphorylation mediated through the visinin-like domain is a new regulatory mechanism for CCaMK activation and calmodulin-dependent protein kinases. Our experiments demonstrate the existence of two functional molecular switches in a protein kinase regulating the kinase activity, namely a visinin-like domain acting as a Ca(2+)-triggered switch and a CaM-binding domain acting as an autophosphorylation-triggered molecular switch.
Document ID
20040141541
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Sathyanarayanan, P. V.
(Washington State University Pullman, Washington 99164-6414, United States)
Cremo, C. R.
Poovaiah, B. W.
Date Acquired
August 22, 2013
Publication Date
September 29, 2000
Publication Information
Publication: The Journal of biological chemistry
Volume: 275
Issue: 39
ISSN: 0021-9258
Subject Category
Life Sciences (General)
Distribution Limits
Public
Copyright
Other
Keywords
NASA Discipline Plant Biology
Non-NASA Center

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