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PDBsum entry 3bs7
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Signaling protein
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PDB id
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3bs7
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References listed in PDB file
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Key reference
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Title
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Cnk and hyp form a discrete dimer by their sam domains to mediate raf kinase signaling.
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Authors
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T.Rajakulendran,
M.Sahmi,
I.Kurinov,
M.Tyers,
M.Therrien,
F.Sicheri.
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Ref.
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Proc Natl Acad Sci U S A, 2008,
105,
2836-2841.
[DOI no: ]
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PubMed id
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Abstract
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RAF kinase functions in the mitogen-activated protein kinase (MAPK) pathway to
transmit growth signals to the downstream kinases MEK and ERK. Activation of RAF
catalytic activity is facilitated by a regulatory complex comprising the
proteins CNK (Connector enhancer of KSR), HYP (Hyphen), and KSR (Kinase
Suppressor of Ras). The sterile alpha-motif (SAM) domain found in both CNK and
HYP plays an essential role in complex formation. Here, we have determined the
x-ray crystal structure of the SAM domain of CNK in complex with the SAM domain
of HYP. The structure reveals a single-junction SAM domain dimer of 1:1
stoichiometry in which the binding mode is a variation of polymeric SAM domain
interactions. Through in vitro and in vivo mutational analyses, we show that the
specific mode of dimerization revealed by the crystal structure is essential for
RAF signaling and facilitates the recruitment of KSR to form the CNK/HYP/KSR
regulatory complex. We present two docking-site models to account for how SAM
domain dimerization might influence the formation of a higher-order CNK/HYP/KSR
complex.
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Figure 1.
The SAM domains of CNK and HYP interact directly. (A) Domain
architecture of CNK and HYP. CNK is characterized by the
presence of a SAM (sterile α-motif) domain; a CRIC (conserved
region in CNK); a PDZ (PSD-95, ZO-1/2, Dlg-1) domain; and a PH
(pleckstrin homology) domain. HYP contains a single SAM domain.
Indicated protein sizes correspond to the Drosophila members.
(B) Pull-down analysis of GST-dHYP^SAM with hCNK2^SAM. GST and
GST-Vts1^SAM served as controls.
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Figure 3.
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