Figure 1.

Column chromatography of crude protein extract from maize coleoptiles. A, The crude protein extract was first desalted on a Sephadex G-25 M column, and then loaded onto a DEAE-Sepharose column. B, The chromatography of step A generated two major peaks; peak 1 was loaded onto a SP Sepharose F.F. column. C, The chromatography of step B generated three major peaks; peak 2 was concentrated and applied to a Sephacryl S-200 column. D, The major peaks obtained in step C were further concentrated and applied to a Sephacryl S-300 column. For A to D, the protein concentration (black circle) in each fraction was monitored by the Bradford Method (Bradford, 1976), and the PTPase activity (white circle) was determined using the [pTyr1018]-EGF receptor as substrate, as described in “Materials and Methods.”