Shinohara, H. and Matsubayashi, Y.
Notes: The authors were looking for a method for ligand fishing experiments with plant receptor-like kinases (RLKs). The strategy chosen, functional immobilization on microbeads, used phytosulfokine (PSK) and its carrot cell receptor (DcPSKR1) as the test ligand-receptor pair. DcPSKR1 was cloned into the pHT2 HaloTag® Vector, adding the HaloTag® gene to the C terminus of DcPSKR1 or replacing the DcPSKR1 kinase domain. These constructs were transfected into BY-2 cells and expression confirmed by immunoblotting the membrane fraction and staining with DcPSKR1 and Anti-HaloTag antibodies. To confirm activity of the individual proteins, membrane fractions of BY-2 cells expressing the DcPSKR1-HaloTag® fusion proteins were tested for PSK binding activity to then HaloTag® binding activity confirmed using the HaloTag® TMR Ligand. The DcPSKR1-ΔKD-Halo protein was immobilized on HaloLink™ Resin and the Kd measured. The binding of PSK to the immobilized DcPSKR1-ΔKD-Halo protein was visualized by using fluorescently labeled Alexa488-PSK. Columns of HaloLink™ Resin with bound DcPSKR1-ΔKD-Halo protein were used to bind PSK ligands at physiological concentration, elute the ligands with a high-salt buffer and analyzed on LC-MS. (3946)