FIG. 3.

Kinase activity of representatives from the HWE HK family. (A) Autophosphorylation of AtExsG, AtBphP2, and SmSMa2063. Recombinant proteins were incubated with [γ-³²P]ATP and separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and the gels were either subjected to autoradiography (left) or stained for protein (right). Asterisks identify contaminants in the SMa2063 protein preparation. Numbers on the left are apparent molecular masses (in kilodaltons) of proteins used to calibrate the gel. (B) The stability of the autophosphorylated form of each after incubation for 2 h at 22°C in 50 mM Tris (pH 7.0), 1 M HCl, or 3 M KOH. (C) Importance of the phosphoacceptor site (His523) and the signature HWE residues (His616, Trp651, and Glu653) to the kinase activity of AtBphP2. Recombinant proteins containing the indicated mutation at each position were tested for kinase activity as described in the legend for panel A. (Top) Autoradiogram; (bottom) protein staining. The positions of the amino acids are indicated in Fig. 1.