Figure 8.

PBK is a serine/threonine kinase. GST-PBK, myelin basic protein (MBP), and histone were phosphorylated in vitro by GST-PBK isolated from okadaic acid-treated Sf9 cells. Autoradiographs of the cellulose plates (EM Science) after separating the proteins on 10% tricine gel, transfer to a poly(vinylidene difluoride) membrane, and phosphoamino acid analysis by two-dimensional electrophoresis (27). Phosphoamino acids from histone (Left), GST-PBK (Center), and MBP (Right) are shown. The traced outlines show where the nonradiolabeled phosphoamino acid standards migrated (phosphoserine, S, phosphothreonine, T, and phosphotyrosine, Y).