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Title: CDK-activating kinase (Ee;CDKF;1) of leafy spurge (Euphorbia esula) forms both homo-dimers and homo-trimers in its native state

item Chao, Wun
item JIA, YING
item Anderson, James

Submitted to: American Society of Plant Biologists Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 4/4/2008
Publication Date: 6/1/2008
Citation: Chao, W.S., Jia, Y., Anderson, J.V. 2008. CDK-activating kinase (Ee;CDKF;1) of leafy spurge (Euphorbia esula) forms both homo-dimers and homo-trimers in its native state. [Abstract] American Society of Plant Biologists Annual Meeting, June 26-July 1, 2008, Merida Mexico. Abs#P27007.

Interpretive Summary:

Technical Abstract: Leafy spurge is a deep rooted perennial weed that propagates both by seeds and underground adventitious buds located on the crown and roots (crown and root buds). As buds develop during the normal growing season, they are maintained in a quiescent state through correlative inhibition. To enhance our understanding of growth and development during seed germination and vegetative propagation, a cell cycle gene encoding CDK-activating kinase (Ee;CDKF;1) was cloned from leafy spurge. The Ee;CDKF;1 protein is involved in a phosphorylation cascade linked to early stages of cell cycle progression. Two threonine residues (Thr291 and Thr296) are mutually responsible for autophosphorylation and for phosphorylating its substrate protein, cyclin-dependent kinase (CDK). Also, Thr291 remains phosphorylated in vivo at all times. Yeast two-hybrid screening performed using Ee;CDKF;1 as a bait indicated that one of the interacting proteins was Ee;CDKF;1. Protein-protein interaction of Ee;CDKF;1 was further confirmed by yeast two-hybrid and in-vitro pull-down assays. The full-length Ee;CDKF;1 was shown to interact with N-terminal, middle, and C-terminal regions of Ee;CDKF;1. Gel exclusion chromatography and native PAGE showed that GST-Ee;CDKF;1 fusion protein was capable of forming both homo-dimer and homo-trimer complexes in its native state. In addition, both forms were autophosphorylated and able to phosphorylate CDK. Although the trimeric form of GST-Ee;CDKF;1 fusion protein is much more abundant than the dimeric form, the activity to phosphorylate its substrate, CDK, appears to be analogous.