This project aims to determine the in vivo cleavage sites of GmPSK4a mediated by GmSBT1.2s via IP-MS/MS. GmSBT1.2b-HA and GmPSK4a-GFP were co-expressed in N. benthamiana and the total protein extract was incubated with GFP affinity beads for 3 hours at 4°C. The purified proteins were then separated by SDS-PAGE, and the specific cleaved products were excised and analyzed by LC-MS/MS to identify the cleavage site.