Isoform-specific localization of A-RAF in mitochondria.
RAF kinase is a family of isoforms including A-RAF, B-RAF, and C-RAF. Despite the important role of RAF in cell growth and proliferation, little evidence exists for isoform-specific function of RAF family members. Using Western analysis and immunogold labeling, A-RAF was selectively localized in highly purified rat liver mitochondria. Two novel human proteins, which interact specifically with A-RAF, were identified, and the full-length sequences are reported. These proteins, referred to as hTOM and hTIM, are similar to components of mitochondrial outer and inner membrane protein-import receptors from lower organisms, implicating their involvement in the mitochondrial transport of A-RAF. hTOM contains multiple tetratricopeptide repeat (TPR) domains, which function in protein-protein interactions. TPR domains are frequently present in proteins involved in cellular transport systems. In contrast, protein 14-3-3, an abundant cytosolic protein that participates in many facets of signal transduction, was found to interact with C-RAF but not with A-RAF N-terminal domain. This information is discussed in view of the important role of mitochondria in cellular functions involving energy balance, proliferation, and apoptosis and the potential role of A-RAF in regulating these systems.
Yuryev
A
A
Novartis Institute for Biomolecular Research, Summit, NJ 07901, USA.
Ono
M
M
Goff
S A
SA
Macaluso
F
F
Wennogle
L P
LP
D048948:14-3-3 Proteins; D000595:Amino Acid Sequence; D000818:Animals; D001692:Biological Transport; D015153:Blotting, Western; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism*; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism*; D008930:Mitochondria, Liver / Q000378:metabolism*; D033681:Mitochondrial Membrane Transport Proteins; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D024101:Mitochondrial Proteins; D008969:Molecular Sequence Data; D020033:Protein Isoforms / Q000378:metabolism; D011506:Proteins / Q000378:metabolism; D019908:Proto-Oncogene Proteins c-raf / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D020449:Repetitive Sequences, Amino Acid; D017386:Sequence Homology, Amino Acid; D020798:Two-Hybrid System Techniques; D014446:Tyrosine 3-Monooxygenase
D048948:14-3-3 Proteins; D002352:Carrier Proteins; D008565:Membrane Proteins; D033681:Mitochondrial Membrane Transport Proteins; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D024101:Mitochondrial Proteins; D020033:Protein Isoforms; D011506:Proteins; D011993:Recombinant Fusion Proteins; C489671:TIMM44 protein, human; C489673:Timm44 protein, rat; D014446:Tyrosine 3-Monooxygenase; D019908:Proto-Oncogene Proteins c-raf