Abstract
The Arabidopsis SOS2 family of twenty-six protein kinases (CIPKs), their interacting activators, the SOS3 family of ten calcium-binding proteins (CBLs) and protein phosphatases type 2C (PP2C), function together in decoding calcium signals elicited by different environmental stimuli. Biochemical data suggest that stable CBL-CIPK or CIPK-PP2C complexes may be regulating the activity of various substrates controlling ion homeostasis. The available structural information provides a general regulatory mechanism in which calcium perception by CBLs and kinase activation is coupled. The structural basis of this molecular mechanism and the specificity of the network is reviewed and discussed in detail.
Highlights
The identification and characterization of the molecular species involved in the mechanisms underlying abiotic stress is crucial to understand and, to control the plant response
phosphatases type 2C (PP2C) ABI2, suggests that SOS2-ABI2 and/or other CIPK-PP2C complexes could act as molecular on-off switches controlling the phosphorylation state of plant ion transporters
The structure shows that the CIPK autoinhibitory FISL motif and the residues involved in PP2C binding are buried in the interface between the CBL and the PPI
Summary
The identification and characterization of the molecular species involved in the mechanisms underlying abiotic stress is crucial to understand and, to control the plant response. PP2C ABI2, suggests that SOS2-ABI2 and/or other CIPK-PP2C complexes could act as molecular on-off switches controlling the phosphorylation state of plant ion transporters In supports to this idea, it has been shown that the 2C-type protein phosphatase AIP1 physically interacts, dephosphorylates and inactivates the AKT1 channel [7,9,10]. The crystal structure of the binary complex of Ca2+-SOS3 with the C-terminal regulatory moiety of SOS2 (Figure 1C) resolved central questions regarding the activation mechanism of CIPKs and the dual function of SOS2 as a kinase and a phosphatase-binding protein. The structure shows that the CIPK autoinhibitory FISL motif and the residues involved in PP2C binding are buried in the interface between the CBL and the PPI domain This provides a molecular mechanism for the CBL mediated activation of the CIPKs and necessarily implies that kinase activation and PP2C binding cannot occur simultaneously. This agrees with the fact that, among the CBLs tested, SOS2 exhibited the strongest interaction with SOS3 [17]
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.
