title: The cysteine-rich region of raf-1 kinase contains zinc, translocates to liposomes, and is adjacent to a segment that binds GTP-ras.
abstract: Different domains of the serine/threonine kinase, raf-1, were expressed as fusion proteins with glutathione S-transferase (GST) in Escherichia coli and purified to near homogeneity by affinity chromatography. A cysteine-rich domain of raf-1 was found to contain 2 mol of zinc (molar basis), similar to analogous cysteine-rich domains of protein kinase C. GST-fusion proteins, containing the cysteine-rich domain of raf-1, bound to liposomes in a phosphatidylserine-dependent manner. In contrast to protein kinase C, the translocation of raf-1 was not dependent upon diacylglycerol, phorbol ester, or calcium, nor did raf-1 bind phorbol esters. A GST-fusion protein encoding residues 1-147 of raf-1 bound to normal GTP-ras with high affinity, but not to mutant GTP-Ala35 ras; no binding was detected to GDP-ras. The binding of a smaller fusion protein (residues 1-130 of raf-1) was about 10-fold weaker, inferring that a 17-amino acid sequence represents a critical binding determinant in intact raf-1. These residues are adjacent to the amino-terminal end of, and partially extend into, the cysteine-rich domain (amino acids 139-184). A synthetic peptide corresponding to this 17-amino acid sequence blocked the interaction of raf-1 with ras. The function of the cysteine-rich region of raf-1 homologous to protein kinase C is to promote translocation of raf-1 kinase to membranes and to form part of the high affinity binding site for GTP-ras.
authors.affiliation: Department of Molecular Cancer Biology, Duke University Medical Center, Durham, North Carolina 27710.
authors.forename: S
authors.initials: S
authors.lastname: Ghosh
authors.forename: W Q
authors.initials: WQ
authors.lastname: Xie
authors.forename: A F
authors.initials: AF
authors.lastname: Quest
authors.forename: G M
authors.initials: GM
authors.lastname: Mabrouk
authors.forename: J C
authors.initials: JC
authors.lastname: Strum
authors.forename: R M
authors.initials: RM
authors.lastname: Bell
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D001665:Binding Sites; D001667:Binding, Competitive; D002118:Calcium / Q000494:pharmacology; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D003001:Cloning, Molecular; D003545:Cysteine; D017931:DNA Primers; D004075:Diglycerides / Q000494:pharmacology; D005982:Glutathione Transferase / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D008081:Liposomes; D008969:Molecular Sequence Data; D010703:Phorbol Esters / Q000494:pharmacology; D016133:Polymerase Chain Reaction; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000737:chemistry* / Q000378:metabolism*; D019908:Proto-Oncogene Proteins c-raf; D016283:Proto-Oncogene Proteins p21(ras) / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D015032:Zinc / Q000032:analysis*
chemical_list: D017931:DNA Primers; D004075:Diglycerides; D008081:Liposomes; D010703:Phorbol Esters; D011518:Proto-Oncogene Proteins; D011993:Recombinant Fusion Proteins; D006160:Guanosine Triphosphate; D005982:Glutathione Transferase; D017346:Protein Serine-Threonine Kinases; D019908:Proto-Oncogene Proteins c-raf; C501009:HRAS protein, human; D016283:Proto-Oncogene Proteins p21(ras); D015032:Zinc; D003545:Cysteine; D002118:Calcium