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

Abstract
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. K i 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.