Phosphorylation Alters the Interaction of the Arabidopsis Phosphotransfer Protein AHP1 with Its Sensor Kinase ETR1
Figure 6
Schematic model of ETR1−AHP1 signaling.
In the absence of ethylene autophosphorylation of the sensor kinase ETR1 ensures low affinity of the receptor to phosphorylated HPt proteins. On the other hand, non-phosphorylated AHP1 binds to the phosphorylated ETR1 receptor with high affinity enabling phosphoryl group transfer to the HPt protein. After ethylene binding the receptor is switched to the non-phosphorylated state. This switch is accompanied by a conformational change that decreases the affinity to the phosphorylated AHP1. The transfer protein, AHP1-P is released and can move to the nucleus for further signal transfer onto response regulator proteins causing gene response. Binding of non-phosphorylated AHP1 to the activated form of the receptor is prevented by the conformational change caused in the receiver domain of the receptor by the binding of the plant hormone.