Abstract
Ras activation of phosphoinositide 3-kinase (PI3K) is important for survival of transformed cells. We find that PI3Kgamma is strongly and directly activated by H-Ras G12V in vivo or by GTPgammaS-loaded H-Ras in vitro. We have determined a crystal structure of a PI3Kgamma/Ras.GMPPNP complex. A critical loop in the Ras binding domain positions Ras so that it uses its switch I and switch II regions to bind PI3Kgamma. Mutagenesis shows that interactions with both regions are essential for binding PI3Kgamma. Ras also forms a direct contact with the PI3Kgamma catalytic domain. These unique Ras/PI3Kgamma interactions are likely to be shared by PI3Kalpha. The complex with Ras shows a change in the PI3K conformation that may represent an allosteric component of Ras activation.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Animals
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Binding Sites
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COS Cells
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Class Ib Phosphatidylinositol 3-Kinase
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Crystallography, X-Ray
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Guanosine 5'-O-(3-Thiotriphosphate) / chemistry
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Guanosine 5'-O-(3-Thiotriphosphate) / metabolism
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Humans
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Isoenzymes / chemistry*
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Isoenzymes / metabolism*
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Kinetics
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Models, Molecular
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Mutagenesis, Site-Directed
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Neutrophils / metabolism
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Phosphatidylinositol 3-Kinases / chemistry*
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Phosphatidylinositol 3-Kinases / genetics
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Phosphatidylinositol 3-Kinases / metabolism*
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Protein Binding
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Protein Conformation
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Protein Structure, Tertiary
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ras Proteins / chemistry
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ras Proteins / metabolism*
Substances
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Isoenzymes
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Guanosine 5'-O-(3-Thiotriphosphate)
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Phosphatidylinositol 3-Kinases
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Class Ib Phosphatidylinositol 3-Kinase
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PIK3CG protein, human
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ras Proteins