FIG. 5.

Recombinant F10 kinase phosphorylates a peptide representing the C terminus of the A17 protein. Recombinant F10 kinase (74 ng) was incubated with [γ-³²P]ATP and various concentrations (0, 5, 10, 50, 100, or 500 μM) of a peptide substrate whose sequence comprised a basic N-terminal extension followed by 10 amino acids representing residues 194 to 203 of the A17 protein. Reactions were performed for 10 or 30 min, as indicated. To quantitate the incorporation of radiolabel, samples were spotted onto P81 paper, washed extensively, and analyzed by Cerenkov counting as described in Materials and Methods.