Inhibition of oncogenic and activated wild-type ras-p21 protein-induced oocyte maturation by peptides from the ras-binding domain of the raf-p74 protein, identified from molecular dynamics calculations.

In the preceding paper we found from molecular dynamics calculations that the structure of the ras-binding domain (RBD) of raf changes predominantly in three regions depending upon whether it binds to ras-p21 or to its inhibitor protein, rap-1A. These three regions of the RBD involve residues from the protein-protein interaction interface, e.g., between residues 60 and 72, residues 97-110, and 111-121. Since the rap-1A-RBD complex is inactive, these three regions are implicated in ras-p21-induced activation of raf. We have therefore co-microinjected peptides corresponding to these three regions, 62-76, 97-110, and 111-121, into oocytes with oncogenic p21 and microinjected them into oocytes incubated in in insulin, which activates normal p21. All three peptides, but not a control peptide, strongly inhibit both oncogenic p21- and insulin-induced oocyte maturation. These findings corroborate our conclusions from the theoretical results that these three regions constitute raf effector domains. Since the 97-110 peptide is the strongest inhibitor of oncogenic p21, while the 111-121 peptide is the strongest inhibitor of insulin-induced oocyte maturation, the possibility exists that oncogenic and activated normal p21 proteins interact differently with the RBD of raf.