v-Ha-Ras insertion/deletion mutants with reduced protease-inhibitory activity have no transforming activity

We have purified 26 insertion/deletion mutants of v-Ha-ras oncogene products produced by Escherichia coli and investigated their protease-inhibitory activity toward papain and cathepsins B and L. Ki values for papain were relatively similar among the mutants, however, those for cathepsins B and L varied up to 10-fold. Among them, four mutants, 1-48 LIR 54-189, 1-110 LIS 112-189, 1-130 PDQ 146-189 and 1-155 LIR 166-189, showed significant reduction in the inhibitory activity toward cathepsin L and these four mutants have lost transforming activity toward NIH3T3 mouse fibroblasts. However, some other mutants also showed no transforming activity in spite of possession of the potent protease-inhibitory activity, suggesting that the protease-inhibitory activity of Ras might be necessary but not sufficient for its biological activity.