Abstract
Binding of brassinolide to the brassinosteroid-insenstive 1(BRI1) receptor kinase promotes interaction with its co-receptor, BRI1-associated receptor kinase 1 (BAK1). Juxtaposition of the kinase domains that occurs then allows reciprocal transphosphorylation and activation of both kinases, but details of that process are not entirely clear. In the present study we show that the carboxy (C)-terminal polypeptide of BAK1 may play a role. First, we demonstrate that the C-terminal domain is a strong inhibitor of the transphosphorylation activity of the recombinant BAK1 cytoplasmic domain protein. However, recombinant BAK1 lacking the C-terminal domain is unable to transactivate the peptide kinase activity of BRI1 in vitro. Thus, the C-terminal domain may play both a positive and negative role. Interestingly, a synthetic peptide corresponding to the full C-terminal domain (residues 576–615 of BAK1) interacted with recombinant BRI1 in vitro, and that interaction was enhanced by phosphorylation at the Tyr-610 site. Expression of a BAK1 C-terminal domain truncation (designated BAK1-ΔCT-Flag) in transgenic Arabidopsis plants lacking endogenous bak1 and its functional paralog, bkk1, produced plants that were wild type in appearance but much smaller than plants expressing full-length BAK1-Flag. The reduction in growth may be attributed to a partial inhibition of BR signaling in vivo as reflected in root growth assays but other factors are likely involved as well. Our working model is that in vivo, the inhibitory action of the C-terminal domain of BAK1 is relieved by binding to BRI1. However, that interaction is not essential for BR signaling, but other aspects of cellular signaling are impacted when the C-terminal domain is truncated and result in inhibition of growth. These results increase the molecular understanding of the C-terminal domain of BAK1 as a regulator of kinase activity that may serve as a model for other receptor kinases.
Highlights
AND RECOMBINANT PROTEIN STUDIESWe show that the C-terminal domain of After sequencing to confirm mutated regions, BRI1-associated receptor kinase 1 (BAK1)-CD and its BAK1 inhibits the transphosphorylation activity of BAK1 but is mutations were expressed in BL21 (DE3) pLysS cells
Reviewed by: Jung-Youn Lee, University of Delaware, USA interaction with its co-receptor, BRI1-associated receptor kinase 1 (BAK1)
The model for plant receptor kinase the kinase domain contains the structures and signaling is based on studies with the receptor kinase, BRI1, and its residues required for phosphoryl transfer from ATP to peptide or co-receptor, BAK1, that together function in brassinosteroid (BR) protein substrates, the flanking domains often play an important signaling
Summary
We show that the C-terminal domain of After sequencing to confirm mutated regions, BAK1-CD and its BAK1 inhibits the transphosphorylation activity of BAK1 but is mutations were expressed in BL21 (DE3) pLysS cells The C-terminal domain is not essential for BR signaling in vivo suggesting that other mechanisms provide proper positioning so that the kinase domains of BRI1 and BAK1 can effectively transphos-. D phorylate and activate the signaling cascade. It is interesting that in the absence of the C-terminal domain of BAK1 plant. E growth is significantly inhibited suggesting that other (presently unknown) factors are affected by removal of the C-terminal domain. T C-terminal domain of BAK1 and perhaps other receptor kinases as well
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
