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PDBsum entry 3hhm
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Transferase/oncoprotein
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PDB id
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3hhm
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References listed in PDB file
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Key reference
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Title
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A frequent kinase domain mutation that changes the interaction between pi3kalpha and the membrane.
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Authors
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D.Mandelker,
S.B.Gabelli,
O.Schmidt-Kittler,
J.Zhu,
I.Cheong,
C.H.Huang,
K.W.Kinzler,
B.Vogelstein,
L.M.Amzel.
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Ref.
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Proc Natl Acad Sci U S A, 2009,
106,
16996-17001.
[DOI no: ]
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PubMed id
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Note: In the PDB file this reference is
annotated as "TO BE PUBLISHED". The citation details given above have
been manually determined.
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Abstract
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Mutations in oncogenes often promote tumorigenesis by changing the conformation
of the encoded proteins, thereby altering enzymatic activity. The PIK3CA
oncogene, which encodes p110alpha, the catalytic subunit of phosphatidylinositol
3-kinase alpha (PI3Kalpha), is one of the two most frequently mutated oncogenes
in human cancers. We report the structure of the most common mutant of p110alpha
in complex with two interacting domains of its regulatory partner (p85alpha),
both free and bound to an inhibitor (wortmannin). The N-terminal SH2 (nSH2)
domain of p85alpha is shown to form a scaffold for the entire enzyme complex,
strategically positioned to communicate extrinsic signals from phosphopeptides
to three distinct regions of p110alpha. Moreover, we found that Arg-1047 points
toward the cell membrane, perpendicular to the orientation of His-1047 in the WT
enzyme. Surprisingly, two loops of the kinase domain that contact the cell
membrane shift conformation in the oncogenic mutant. Biochemical assays revealed
that the enzymatic activity of the p110alpha His1047Arg mutant is differentially
regulated by lipid membrane composition. These structural and biochemical data
suggest a previously undescribed mechanism for mutational activation of a kinase
that involves perturbation of its interaction with the cellular membrane.
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Figure 2.
The nSH2 domain of p85α forms a scaffold for the PI3Kα
enzyme. (A) p85α nSH2 acts as a scaffold and interacts with the
p85α iSH2 domain as well as the p110α kinase, helical, and C2
domains. (B) The nSH2 αA helix fits into a crevice between the
C2 and kinase domains. (C) nSH2 interactions with the p110α C2
domain. (D) Residue-residue interactions between nSH2 and the
helical and kinase domains.
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Figure 3.
Interactions between p110α and p85 nSH2. (A) Ribbon diagram
of nSH2, helical, and kinase domains determined from the
structure reported in this work. (B) The same ribbon diagram as
in A but showing the position of the PDGFR phosphopeptide (gray)
modeled as in PDB ID code 2IUI, at the interface between nSH2
and the helical domain. The loop of the helical domain occupies
nearly the same position as the phosphopeptide, so their
occurrence is mutually exclusive. (C) The phosphopeptide is
predicted to disrupt the interaction between the positively
charged nSH2 surface (shaded blue) and the negatively charged
helical domain residues. The phosphopeptide is shown in gray,
with its phosphotyrosine in stick and ball representation and
the phosphate shaded red. The boxed region shows that the side
chain of Glu-542 occupies the space usually occupied by the
phosphate of the peptide's phosphotyrosine residue.
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