1kbf
Solution Structure of the Cysteine-Rich C1 Domain of Kinase Suppressor of Ras
Structural highlights
FunctionKSR1_MOUSE Location-regulated scaffolding protein connecting MEK to RAF. Promotes MEK and RAF phosphorylation and activity through assembly of an activated signaling complex. By itself, it has no demonstrated kinase activity. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedKinase suppressor of Ras (KSR) is a conserved component of the Ras pathway that acts as a molecular scaffold to promote signal transmission from Raf-1 to MEK and MAPK. All KSR proteins contain a conserved cysteine-rich C1 domain, and studies have implicated this domain in the regulation of KSR1 subcellular localization and function. To further elucidate the biological role of the KSR1 C1 domain, we have determined its three-dimensional solution structure using nuclear magnetic resonance (NMR). We find that while the overall topology of the KSR1 C1 domain is similar to the C1 domains of Raf-1 and PKCgamma, the predicted ligand-binding region and the surface charge distribution are unique. Moreover, by generating chimeric proteins in which these domains have been swapped, we find that the C1 domains of Raf-1, PKCgamma, and KSR1 are not functionally interchangeable. The KSR1 C1 domain does not bind with high affinity or respond biologically to phorbol esters or ceramide, and it does not interact directly with Ras, indicating that the putative ligand(s) for the KSR1 C1 domain are distinct from those that interact with PKCgamma and Raf-1. In addition, our analysis of the chimeric proteins supports the model that Raf-1 is a ceramide-activated kinase and that its C1 domain is involved in the ceramide-mediated response. Finally, our findings demonstrate an absolute requirement of the KSR1 C1 domain in mediating the membrane localization of KSR1, a crucial feature of its scaffolding activity. Together, these results underscore the functional specificity of these important regulatory domains and demonstrate that the structural features of the C1 domains can provide valuable insight into their ligand-binding properties. Solution structure and functional analysis of the cysteine-rich C1 domain of kinase suppressor of Ras (KSR).,Zhou M, Horita DA, Waugh DS, Byrd RA, Morrison DK J Mol Biol. 2002 Jan 18;315(3):435-46. PMID:11786023[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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