Identification of functional domains in the neuronal Cdk5 activator protein.
Cyclin-dependent kinase 5 (Cdk5) is activated by the neuronal-specific activator protein, p35. In contrast to the activation of typical CDKs by cyclin subunits, p35.Cdk5 was not further activated by the CDK-activating kinase (CAK) and was neither phosphorylated nor inhibited by the Tyr-15-specific Wee1 kinase. The previously identified proteolytic active fragment of p35, p25 (residues 91-307) as well as the slightly smaller fragment containing residues 109-291, was found to be sufficient to bind and activate Cdk5. Other CDKs, including Cdk2, associated weakly with p25. However, their kinase activity was only activated to the low level observed for cyclin A.Cdk2 without Thr-160 phosphorylation, and phosphorylation of Thr-160 in Cdk2 did not activate the p25.Cdk2 complex further. We have identified distinct regions in p35 required for binding to Cdk5 or activation of Cdk5. Residues approximately 150-200 of p35 were sufficient for binding to Cdk5, but residues approximately 279-291 were needed in addition for activation of Cdk5 in vitro.
Poon
R Y
RY
Salk Institute for Biological Studies, La Jolla, California 92037, USA.
Lew
J
J
Hunter
T
T
D000818:Animals; D018797:Cell Cycle Proteins; D051360:Cyclin-Dependent Kinase 5; D018844:Cyclin-Dependent Kinases; D004789:Enzyme Activation; D006801:Humans; D051379:Mice; D009419:Nerve Tissue Proteins / Q000737:chemistry* / Q000235:genetics; D009474:Neurons / Q000737:chemistry*; D009687:Nuclear Proteins; D011487:Protein Conformation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D017384:Sequence Deletion; D014981:Xenopus; D029867:Xenopus Proteins
D018797:Cell Cycle Proteins; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; D029867:Xenopus Proteins; C089495:neuronal Cdk5 activator (p25-p35); C530005:WEE1 protein, Xenopus; D011505:Protein-Tyrosine Kinases; C499349:WEE1 protein, human; C499348:Wee1 protein, mouse; D051360:Cyclin-Dependent Kinase 5; D017346:Protein Serine-Threonine Kinases; C495905:CDK5 protein, human; C495908:Cdk5 protein, Xenopus; C495906:Cdk5 protein, mouse; D018844:Cyclin-Dependent Kinases