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Proc Natl Acad Sci U S A. 1996 Dec 10;93(25):14373-8.

Crystal structure of the breakpoint cluster region-homology domain from phosphoinositide 3-kinase p85 alpha subunit.

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Laboratory of Molecular Medicine, Children's Hospital, Boston, MA 02115, USA.


Proteins such as the product of the break-point cluster region, chimaerin, and the Src homology 3-binding protein 3BP1, are GTPase activating proteins (GAPs) for members of the Rho subfamily of small GTP-binding proteins (G proteins or GTPases). A 200-residue region, named the breakpoint cluster region-homology (BH) domain, is responsible for the GAP activity. We describe here the crystal structure of the BH domain from the p85 subunit of phosphatidylinositol 3-kinase at 2.0 A resolution. The domain is composed of seven helices, having a previously unobserved arrangement. A core of four helices contains most residues that are conserved in the BH family. Their packing suggests the location of a G-protein binding site. This structure of a GAP-like domain for small GTP-binding proteins provides a framework for analyzing the function of this class of molecules.

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