Novel protein kinases associated with calcineurin B-like calcium sensors in Arabidopsis.
Members of the Arabidopsis calcineurin B-like Ca(2)+ binding protein (AtCBL) family are differentially regulated by stress conditions. One AtCBL plays a role in salt stress; another is implicated in response to other stress signals, including drought, cold, and wounding. In this study, we identified a group of novel protein kinases specifically associated with AtCBL-type Ca(2)+ sensors. In addition to a typical protein kinase domain, they all contain a unique C-terminal region that is both required and sufficient for interaction with the AtCBL-type but not calmodulin-type Ca(2)+ binding proteins from plants. Interactions between the kinases and AtCBLs require micromolar concentrations of Ca(2)+, suggesting that increases in cellular Ca(2)+ concentrations may trigger the formation of AtCBL-kinase complexes in vivo. Unlike most serine/threonine kinases, the AtCBL-interacting kinase efficiently uses Mn(2)+ to Mg(2)+ as a cofactor and may function as a Mn(2)+ binding protein in the cell. These findings link a new type of Ca(2)+ sensors to a group of novel protein kinases, providing the molecular basis for a unique Ca(2)+ signaling machinery in plant cells.
Shi
J
J
Department of Plant and Microbial Biology, University of California, Berkeley, California 94720, USA.
Kim
K N
KN
Ritz
O
O
Albrecht
V
V
Gupta
R
R
Harter
K
K
Luan
S
S
Kudla
J
J
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000378:metabolism*; D029681:Arabidopsis Proteins; D001665:Binding Sites; D019703:Calcineurin / Q000378:metabolism*; D002118:Calcium / Q000502:physiology*; D020013:Calcium Signaling / Q000502:physiology*; D002135:Calcium-Binding Proteins / Q000737:chemistry* / Q000378:metabolism*; D008969:Molecular Sequence Data; D010766:Phosphorylation; D011494:Protein Kinases / Q000737:chemistry* / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
D029681:Arabidopsis Proteins; C417306:CBL protein, Arabidopsis; D002135:Calcium-Binding Proteins; D011994:Recombinant Proteins; D011494:Protein Kinases; D019703:Calcineurin; D002118:Calcium