2byv
From Proteopedia
Structure of the cAMP responsive exchange factor Epac2 in its auto- inhibited state
Structural highlights
FunctionRPGF4_MOUSE Guanine nucleotide exchange factor (GEF) for RAP1A, RAP1B and RAP2A small GTPases that is activated by binding cAMP. Seems not to activate RAB3A. Involved in cAMP-dependent, PKA-independent exocytosis through interaction with RIMS2.[1] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedEpac proteins (exchange proteins directly activated by cAMP) are guanine-nucleotide-exchange factors (GEFs) for the small GTP-binding proteins Rap1 and Rap2 that are directly regulated by the second messenger cyclic AMP and function in the control of diverse cellular processes, including cell adhesion and insulin secretion. Here we report the three-dimensional structure of full-length Epac2, a 110-kDa protein that contains an amino-terminal regulatory region with two cyclic-nucleotide-binding domains and a carboxy-terminal catalytic region. The structure was solved in the absence of cAMP and shows the auto-inhibited state of Epac. The regulatory region is positioned with respect to the catalytic region by a rigid, tripartite beta-sheet-like structure we refer to as the 'switchboard' and an ionic interaction we call the 'ionic latch'. As a consequence of this arrangement, the access of Rap to the catalytic site is sterically blocked. Mutational analysis suggests a model for cAMP-induced Epac activation with rigid body movement of the regulatory region, the features of which are universally conserved in cAMP-regulated proteins. Structure of the cyclic-AMP-responsive exchange factor Epac2 in its auto-inhibited state.,Rehmann H, Das J, Knipscheer P, Wittinghofer A, Bos JL Nature. 2006 Feb 2;439(7076):625-8. PMID:16452984[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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