2y4i

From Proteopedia

KSR2-MEK1 heterodimer

Structural highlights

2y4i is a 2 chain structure with sequence from Homo sapiens and Oryctolagus cuniculus. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance.
Method:	X-ray diffraction, Resolution 3.46Å
Ligands:	, ,
Resources:	FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT

Function

KSR2_HUMAN

Publication Abstract from PubMed

In metazoans, the Ras-Raf-MEK (mitogen-activated protein-kinase kinase)-ERK (extracellular signal-regulated kinase) signalling pathway relays extracellular stimuli to elicit changes in cellular function and gene expression. Aberrant activation of this pathway through oncogenic mutations is responsible for a large proportion of human cancer. Kinase suppressor of Ras (KSR) functions as an essential scaffolding protein to coordinate the assembly of Raf-MEK-ERK complexes. Here we integrate structural and biochemical studies to understand how KSR promotes stimulatory Raf phosphorylation of MEK (refs 6, 7). We show, from the crystal structure of the kinase domain of human KSR2 (KSR2(KD)) in complex with rabbit MEK1, that interactions between KSR2(KD) and MEK1 are mediated by their respective activation segments and C-lobe alphaG helices. Analogous to BRAF (refs 8, 9), KSR2 self-associates through a side-to-side interface involving Arg 718, a residue identified in a genetic screen as a suppressor of Ras signalling. ATP is bound to the KSR2(KD) catalytic site, and we demonstrate KSR2 kinase activity towards MEK1 by in vitro assays and chemical genetics. In the KSR2(KD)-MEK1 complex, the activation segments of both kinases are mutually constrained, and KSR2 adopts an inactive conformation. BRAF allosterically stimulates the kinase activity of KSR2, which is dependent on formation of a side-to-side KSR2-BRAF heterodimer. Furthermore, KSR2-BRAF heterodimerization results in an increase of BRAF-induced MEK phosphorylation via the KSR2-mediated relay of a signal from BRAF to release the activation segment of MEK for phosphorylation. We propose that KSR interacts with a regulatory Raf molecule in cis to induce a conformational switch of MEK, facilitating MEK's phosphorylation by a separate catalytic Raf molecule in trans.

A Raf-induced allosteric transition of KSR stimulates phosphorylation of MEK.,Brennan DF, Dar AC, Hertz NT, Chao WC, Burlingame AL, Shokat KM, Barford D Nature. 2011 Apr 21;472(7343):366-9. Epub 2011 Mar 27. PMID:21441910^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

References

↑ Brennan DF, Dar AC, Hertz NT, Chao WC, Burlingame AL, Shokat KM, Barford D. A Raf-induced allosteric transition of KSR stimulates phosphorylation of MEK. Nature. 2011 Apr 21;472(7343):366-9. Epub 2011 Mar 27. PMID:21441910 doi:10.1038/nature09860