Involvement of B-Raf in Ras-induced Raf-1 activation.
The mechanism of Ras-induced Raf-1 activation is not fully understood. Previously, we identified a 400-kDa protein complex as a Ras-dependent Raf-1 activator. In this study, we identified B-Raf as a component of this complex. B-Raf was concentrated during the purification of the activator. Immunodepletion of B-Raf abolished the effect of the activator on Raf-1. Furthermore, B-Raf and Ras-activated Raf-1 co-operatively, when co-transfected into human embryonic kidney 293 cells. On the other hand, Ras-dependent extracellular signal-regulated kinase/mitogen-activated protein kinase kinase stimulator (a complex of B-Raf and 14-3-3) failed to activate Raf-1 in our cell-free system. These results suggest that B-Raf is an essential component of the Ras-dependent Raf-1 activator.
Mizutani
S
S
Faculty of Bioscience and Biotechnology, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, 226-8501, Yokohama, Japan.
Inouye
K
K
Koide
H
H
Kaziro
Y
Y
D002478:Cells, Cultured; D006801:Humans; D048493:Proto-Oncogene Proteins B-raf; D019908:Proto-Oncogene Proteins c-raf / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D014162:Transfection; D018631:ras Proteins / Q000378:metabolism*
D048493:Proto-Oncogene Proteins B-raf; D019908:Proto-Oncogene Proteins c-raf; D018631:ras Proteins