Detection of 210 kDa receptor protein for a leaf-movement factor by using novel photoaffinity probes

Circadian rhythmic plant leaf-movement, called nyctinasty, is controlled by a time-course change in the internal concentration of the leaf-movement factor in the plant body. We revealed that specific binding proteins (210 and 180 kDa) for the leaf-movement factor, potassium lespedezate (1), are contained in the plasma membrane of the plant motor cell by using novel synthetic photoaffinity probes. These proteins are localized on the motor cell in the plant body, and would be potential receptors for the leaf-movement factor to control the leaf-movement. Our study is a rare successful result of the detection of membrane receptors by using a synthetic photoaffinity probe designed on a biologically active natural product. And these results also advance a guideline for probe design towards successful photoaffinity labeling.