PDBsum entry 3hiz

Transferase/oncoprotein

PDB id: 3hiz

Contents

Protein chains

1024 a.a.

234 a.a.

References listed in PDB file

Key reference

Title

A frequent kinase domain mutation that changes the interaction between pi3kalpha and the membrane.

Authors

D.Mandelker, S.B.Gabelli, O.Schmidt-Kittler, J.Zhu, I.Cheong, C.H.Huang, K.W.Kinzler, B.Vogelstein, L.M.Amzel.

Ref.

Proc Natl Acad Sci U S A, 2009, 106, 16996-17001. [DOI no: 10.1073/pnas.0908444106]

PubMed id

19805105

Note: In the PDB file this reference is annotated as "TO BE PUBLISHED". The citation details given above have been manually determined.

Abstract

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.

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.

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.