Table I. Purification of ZmRIP1 from maize coleoptiles.

Purification was performed as described in “Materials and Methods.” For a single preparation, 150 g of coleoptile was used. Protein was determined by the Bradford Method (Bradford, 1976), and PTPase activity was determined using [pTyr¹⁰¹⁸]-EGF receptor as substrate.

Step	Total Protein	Specific Activity	Fold
	mg	mmol min−1 mg−1
Triton extract	1,267	0.36	1
DEAE column	218	2.11	6
SP-Sepharose	17.2	63	175
Sephacryl S-200	0.12	325	541
Sephacryl S-300	<0.02	580	1,611