CDPKs are dual-specificity protein kinases and tyrosine autophosphorylation attenuates kinase activity.
Although calcium-dependent protein kinases (CDPKs or CPKs) are classified as serine/threonine protein kinases, autophosphorylation on tyrosine residues was observed for soybean CDPKβ and several Arabidopsis isoforms (AtCPK4 and AtCPK34). We identified Ser-8, Thr-17, Tyr-24 (in the kinase domain), Ser-304, and Ser-358 as autophosphorylation sites of His(6)-GmCDPKβ. Overall autophosphorylation increased kinase activity with synthetic peptides, but autophosphorylation of Tyr-24 appears to attenuate kinase activity based on studies with the Y24F directed mutant. While much remains to be done, it is clear that several CDPKs are dual-specificity kinases, which raises the possibility that phosphotyrosine signaling may play a role in Ca(2+)/CDPK-mediated processes.
Department of Plant Biology, University of Illinois, Urbana, IL 61801, USA.
Man-Ho
MH
Oh
Xia
X
Wu
Hyoung Seok
HS
Kim
Jeffrey F
JF
Harper
Raymond E
RE
Zielinski
Steven D
SD
Clouse
Steven C
SC
Huber
D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D015151:Immunoblotting; D013058:Mass Spectrometry; D016297:Mutagenesis, Site-Directed; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism*; D012694:Serine / Q000378:metabolism; D053719:Tandem Mass Spectrometry; D013912:Threonine / Q000378:metabolism; D014443:Tyrosine / Q000378:metabolism*
D029681:Arabidopsis Proteins; D002135:Calcium-Binding Proteins; D011994:Recombinant Proteins; D013912:Threonine; D014443:Tyrosine; D012694:Serine; D017346:Protein Serine-Threonine Kinases; D002118:Calcium