""""""""ras oncogenes are frequently associated with human cancer and activated forms of ras are powerfully transforming in experimental systems. Ras proteins control multiple signaling pathways via multiple effectors. The mechanisms by which those effectors are activated by Ras remain unclear. We are investigating the molecular mechanism by which the Ras proteins activate the Raf kinase class of effectors. The ultimate aim of these studies is to allow the design of highly specific small molecule inhibitors of Raf activation. we have found that Ras activates Raf by binding to two distinct sites on Raf. Both binding interactions are crtitical in generating a fully activated Raf molecule. we have identified specific residues within the second Ras binding domain which are essential for Ras interaction. Moreover, we have characterized the interplay of 14-3-3 and Phosphatidylserine as co-factors in the Ras mediated activation of Raf. We are currently investigating the possibility that Ras serves to release the c-terminal kinase domain of Raf from inhibitory, intramolecular binding contacts in the n-terminal, regulatory doamin of Raf, and whether 14-3-3 may serve as a bridge in such an interaction. we intend to extend these studies to compare the regulation of the B-isoform of Raf with that of the c isoform. Lesons learned formn the activation of raf by ras may be extapolated to other classes of Ras effectors.""""""""
