Phosphorylation of BES1/BZR1 by BIN2 in vitro. A,
BIN2 can phosphorylate both BES1 and BZR1 in vitro. GST-BES1 (top) or
GST-BZR1 (bottom) fusion proteins were mixed with the wild-type BIN2
(lane 1), the Lys-69-Arg-mutated GST-BIN2 (lane 2), or the
bin2-1-mutated GST-BIN2 (lane 3) to measure protein
phosphorylation activity as described in “Materials and Methods.”
B, GST-BRI1CK was unable to phosphorylate BES1 or BZR1 protein. C, The
phosphorylation of BES1 or BZR1 by BIN2 can be inhibited by lithium.
For A through C, the amount of proteins used in the kinase assays is
indicated by Coomassie Blue staining in the top strip above the white
dividing line, whereas the level of proteins phosphorylation is shown
by autoradiography in the bottom strip.