Activation of the plasma membrane Na/H antiporter Salt-Overly-Sensitive 1 (SOS1) by phosphorylation of an auto-inhibitory C-terminal domain.
The plasma membrane sodium/proton exchanger Salt-Overly-Sensitive 1 (SOS1) is a critical salt tolerance determinant in plants. The SOS2-SOS3 calcium-dependent protein kinase complex up-regulates SOS1 activity, but the mechanistic details of this crucial event remain unresolved. Here we show that SOS1 is maintained in a resting state by a C-terminal auto-inhibitory domain that is the target of SOS2-SOS3. The auto-inhibitory domain interacts intramolecularly with an adjacent domain of SOS1 that is essential for activity. SOS1 is relieved from auto-inhibition upon phosphorylation of the auto-inhibitory domain by SOS2-SOS3. Mutation of the SOS2 phosphorylation and recognition site impeded the activation of SOS1 in vivo and in vitro. Additional amino acid residues critically important for SOS1 activity and regulation were identified in a genetic screen for hypermorphic alleles.
Instituto de Recursos Naturales y Agrobiologia, Consejo Superior de Investigaciones Cientificas, 41012 Sevilla, Spain.
Francisco J
FJ
Quintero
Juliana
J
Martinez-Atienza
Irene
I
Villalta
Xingyu
X
Jiang
Woe-Yeon
WY
Kim
Zhair
Z
Ali
Hiroaki
H
Fujii
Imelda
I
Mendoza
Dae-Jin
DJ
Yun
Jian-Kang
JK
Zhu
Jose M
JM
Pardo
D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D010766:Phosphorylation / Q000502:physiology; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary; D017923:Sodium-Hydrogen Exchangers / Q000235:genetics / Q000378:metabolism*
D029681:Arabidopsis Proteins; C477653:SOS1 protein, Arabidopsis; C112941:SOS3 protein, Arabidopsis; D017923:Sodium-Hydrogen Exchangers; C406738:SOS2 protein, Arabidopsis; D017346:Protein Serine-Threonine Kinases
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