SCaBP1 and SCaBP6 specifically activate PKS24. Kinase assays were performed using combinations of GST-PKS24, GST-SOS2, or His-PKS5 and GST-SCaBP1, GST-SCaBP6, or GST-SCaBP8 as indicated. Coomassie Blue-stained polyacrylamide gel (top); phosphorylation activity (bottom). PKS24, SOS2, SCaBP1, SCaBP6, and SCaBP8 were fused to GST tag; PKS5 was fused to His tag. SC1, SCaBP1; SC6, SCaBP6; SC8, SCaBP8.