title: The solution structure of the Raf-1 cysteine-rich domain: a novel ras and phospholipid binding site.
abstract: The Raf-1 protein kinase is the best-characterized downstream effector of activated Ras. Interaction with Ras leads to Raf-1 activation and results in transduction of cell growth and differentiation signals. The details of Raf-1 activation are unclear, but our characterization of a second Ras-binding site in the cysteine-rich domain (CRD) and the involvement of both Ras-binding sites in effective Raf-1-mediated transformation provides insight into the molecular aspects and consequences of Ras-Raf interactions. The Raf-1 CRD is a member of an emerging family of domains, many of which are found within signal transducing proteins. Several contain binding sites for diacylglycerol (or phorbol esters) and phosphatidylserine and are believed to play a role in membrane translocation and enzyme activation. The CRD from Raf-1 does not bind diacylglycerol but interacts with Ras and phosphatidylserine. To investigate the ligand-binding specificities associated with CRDs, we have determined the solution structure of the Raf-1 CRD using heteronuclear multidimensional NMR. We show that there are differences between this structure and the structures of two related domains from protein kinase C (PKC). The differences are confined to regions of the CRDs involved in binding phorbol ester in the PKC domains. Since phosphatidylserine is a common ligand, we expect its binding site to be located in regions where the structures of the Raf-1 and PKC domains are similar. The structure of the Raf-1 CRD represents an example of this family of domains that does not bind diacylglycerol and provides a framework for investigating its interactions with other molecules.
authors.affiliation: Department of Biochemistry and Biophysics, Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill 27599, USA.
authors.forename: H R
authors.initials: HR
authors.lastname: Mott
authors.forename: J W
authors.initials: JW
authors.lastname: Carpenter
authors.forename: S
authors.initials: S
authors.lastname: Zhong
authors.forename: S
authors.initials: S
authors.lastname: Ghosh
authors.forename: R M
authors.initials: RM
authors.lastname: Bell
authors.forename: S L
authors.initials: SL
authors.lastname: Campbell
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D003545:Cysteine / Q000737:chemistry; D006860:Hydrogen Bonding; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010743:Phospholipids / Q000378:metabolism; D011485:Protein Binding; D011493:Protein Kinase C / Q000737:chemistry; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry*; D017433:Protein Structure, Secondary; D011518:Proto-Oncogene Proteins / Q000737:chemistry*; D019908:Proto-Oncogene Proteins c-raf; D011994:Recombinant Proteins; D016415:Sequence Alignment; D012996:Solutions
chemical_list: D010743:Phospholipids; D011518:Proto-Oncogene Proteins; D011994:Recombinant Proteins; D012996:Solutions; D017346:Protein Serine-Threonine Kinases; D019908:Proto-Oncogene Proteins c-raf; D011493:Protein Kinase C; D003545:Cysteine