Figure 4.

Biochemical characterization of ZmRIP1. A, ZmRIP1 was expressed in and purified from yeast cells and the enzyme activity was assayed with and without the addition of the indicated effectors to the reaction buffer. Key: IR, [pTyr1146]-insulin receptor; ER, [pTyr1018]-EGF receptor; PT, phosphotyrosine; pNPP, p-nitrophenyl phosphate. B to E, ZmRIP1 was expressed in and purified from yeast cells and the enzymatic activity was determined using [pTyr1018]-EGF receptor as substrate. Various effectors were either added or not to the reaction buffer. Values are means ± se of four samples. F, Twenty minutes after the reaction started, DTT was either added (white circle) or not (black circle; i.e. control) to the reaction mixture and, after another 10 min, H₂O₂ was added to the reaction mixture. Values are means ± se of four samples.