The effect of posttranslational modifications on the interaction of Ras2 with adenylyl cyclase.

Ras proteins undergo a series of posttranslational modifications that are critical for their cellular function. These modifications are necessary to anchor Ras proteins to the membrane. Yeast Ras2 proteins were purified with various degrees of modification and examined for their ability to activate their effector, adenylyl cyclase. The farnesylated intermediate form of Ras2 had more than 100 times higher affinity for adenylyl cyclase than for the unprocessed form. The subsequent palmitoylation reaction had little effect. In contrast, palmitoylation was required for efficient membrane localization of the Ras2 protein. These results indicate the importance of farnesylation in the interaction of Ras2 with its effector.