Figure 4.

Progesterone-stimulated phosphorylation of XCL100(C260S) on threonine 168. (A) In vivo radiolabeling of XCL100(C260S) proteins mutated at Thr 168. Stage VI oocytes were microinjected with mRNA (50 ng) encoding Myc-tagged XCL100(C260S) or XCL100(C260S) having its threonine 168 residue mutated to valine (T168V) or glutamate (T168E). Oocytes were immediately transferred to phosphate-free OR2 containing 1 mCi/ml [³²P]orthophosphate and processed as described in Figure 2C. (B) Phosphoamino acid analysis of radiolabeled XCL100(C260S) proteins was carried out as detailed in Figure 2D.