Activation of Brain B-Raf Protein Kinase by Rap1B Small GTP-binding Protein

• DOI: 10.1074/jbc.271.3.1258
• Publication Date: 2002-07-26T14:52:05Z
• Authors: Toshihisa Ohtsuka; Kazuya Shimizu; Bunpei Yamamori; Shinya Kuroda; Yoshimi Takai
• Keywords: Rap1; c-Raf; ASK1

Rap1 small GTP-binding protein has the same amino acid sequence at its effector domain as that of Ras. been shown to antagonize Ras functions, such Ras-induced transformation NIH 3T3 cells and activation c-Raf-1 kinase-dependent mitogen-activated (MAP) kinase cascade in Rat-1 cells, whereas we have well stimulates DNA synthesis Swiss cells. We established a cell-free assay system which activates bovine brain B-Raf kinase. Here used this examined effect on activity phosphorylate recombinant MAP (MEK). Recombinant Rap1B stimulated B-Raf, was partially purified from immunoprecipitated by an anti-B-Raf antibody. The GTP-bound form active, but GDP-bound inactive. fully post-translationally lipid-modified unmodified nearly maximum Ki-Ras. enhanced Ki-Ras-stimulated additive manner. These results indicate not only also is involved B-Raf-dependent cascade.