title: Calcium-regulated protein kinases of plants.
abstract: The importance of calcium ions in coupling physiological responses to external and developmental signals in plants has been well documented. Recently, Plieth and Trewavas (Plant Physiology, 2002, 129: 786-796) have shown that gravistimulation, too, elicits changes in the concentration of cytoplasmic Ca2+ in Arabidopsis plants. Cytoplasmic calcium brings about responses by interacting with target proteins, many of which contain EF-hand calcium-binding motifs. In plants there are at least five classes of protein kinases, all of which are in the CDPK/SnRK family, that either contain EF-hands within their structure or interact with proteins that contain EF-hands. Calcium-dependent protein kinases (CDPKs) and calcium and calmodulin-activated protein kinases (CCaMKs) both contain EF hands in their C-terminal domains and are activated by the binding of calcium. SnRK3s (Group 3 of the SNF-1 related kinases) bind to proteins that contain three EF hands, and some are activated by calcium. Members of two other protein kinase classes, plant calmodulin-dependent protein kinase (CaMK) and CDPK-related kinase (CRK), bind to calmodulin, but it remains to be seen whether the activity of these enzymes is regulated by calcium/calmodulin. This paper will review what is known about the structure and the regulation of these protein kinases and address the question of why there is such a plethora of calcium-regulated kinases in plants.
authors.affiliation: Department of Botany, University of Florida, Gainesville, FL, USA. Harmon@botany.ufl.edu
authors.forename: Alice C
authors.initials: AC
authors.lastname: Harmon
mesh_terms: D017360:Arabidopsis; D002118:Calcium / Q000378:metabolism / Q000502:physiology*; D015220:Calcium Channels / Q000378:metabolism / Q000502:physiology; D002135:Calcium-Binding Proteins / Q000145:classification* / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D002147:Calmodulin / Q000378:metabolism / Q000502:physiology; D018521:Plant Physiological Phenomena; D010940:Plant Proteins / Q000145:classification / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D011494:Protein Kinases / Q000145:classification* / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology*
chemical_list: D015220:Calcium Channels; D002135:Calcium-Binding Proteins; D002147:Calmodulin; D010940:Plant Proteins; D011494:Protein Kinases; D002118:Calcium