Phosphorylation of ARC1. The functional SRK-910 kinase domain (GSTkinase910, lanes 1–3), the inactive form (GSTmukinase910, lanes 4 and 5), the Arabidopsis RLK5 kinase domain (GSTkinaseRLK5, lanes 6–8), or the SRK-A14 kinase domain (GSTkinaseA14, lanes 9–11) were mixed with either GST or GSTARC1 to examine phosphorylation. Lanes 1, 4, 6, and 9 contain the kinases alone. GSTARC1 is present in lanes 2, 5, 7, and 10. GST alone is in lanes 3, 8, and 9. No phosphorylation of GST is seen, but a clear phosphorylation of GSTARC1 is detected in the presence of GSTkinase910 and GSTkinaseA14. The asterisks mark the position of the GSTARC1 protein, and the dots mark the position of the GST protein detected by Coomassie Blue staining. The predicted sizes of the proteins are GSTARC1 (full length) fusion protein, 99 kDa; GSTkinase910, 71 kDa; GSTmukinase910, 71 kDa; GSTkinaseRLK5, 65 kDa; and GSTkinaseA14, 70 kDa.