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Structure and regulation of the cAMP-binding domains of Epac2

Nature Structural Biology volume 10, pages 26–32 (2003)Cite this article

Abstract

Cyclic adenosine monophosphate (cAMP) is a universal second messenger that, in eukaryotes, was believed to act only on cAMP-dependent protein kinase A (PKA) and cyclic nucleotide-regulated ion channels. Recently, guanine nucleotide exchange factors specific for the small GTP-binding proteins Rap1 and Rap2 (Epacs) were described, which are also activated directly by cAMP. Here, we have determined the three-dimensional structure of the regulatory domain of Epac2, which consists of two cyclic nucleotide monophosphate (cNMP)-binding domains and one DEP (Dishevelled, Egl, Pleckstrin) domain. This is the first structure of a cNMP-binding domain in the absence of ligand, and comparison with previous structures, sequence alignment and biochemical experiments allow us to delineate a mechanism for cyclic nucleotide-mediated conformational change and activation that is most likely conserved for all cNMP-regulated proteins. We identify a hinge region that couples cAMP binding to a conformational change of the C-terminal regions. Mutations in the hinge of Epac can uncouple cAMP binding from its exchange activity.

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Figure 1: Structure of Epac.
Figure 2: Ribbon diagram of the DEP domains of Epac and Dishevelled.
Figure 3: Comparison of cAMP-binding domains of Epac (cAMP-free) and PKAs (cAMP-bound).
Figure 4: Biochemical analysis of the regulation mechanism of Epac.

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Protein Data Bank

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Acknowledgements

We thank I. Vetter, I. Schlichting, M. Weyand and A. Scheidig for help during data collection and interesting discussions. We thank D. Kuehlmann, C. Koerner and A. Gerhards for excellent technical support, R. Schebaum for secretarial assistance and M. Würtele and M. Hess for help with figure preparation. We thank the staff of ESRF Grenoble, particularly M. Roth, for beam time allocation and assistance with X-ray data collection. H.R. was supported by a grant from the Council of Earth and Life Science of the Netherlands Organization for Scientific Research (NWO-ALW) and B.P. from an HFSP grant to A.W.

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Author notes

  1. Balaji Prakash

    Present address: Department of Biological Sciences and Bio-Engineering, Indian Institute of Technology, Kanpur, 208 016, India

  2. Holger Rehmann, Balaji Prakash, Eva Wolf, Johan de Rooij and Johannes L. Bos: These authors contributed equally to this work.

Authors and Affiliations

  1. Max-Planck Institut für Molekulare Physiologie, Otto Hahn Strasse 11, Dortmund, D-44227, Germany

    Holger Rehmann, Balaji Prakash, Eva Wolf, Alma Rueppel & Alfred Wittinghofer

  2. Department of Physiological Chemistry and Center for Biomedical Genetics, University Medical Centre Utrecht, Universiteitsweg 100, Utrecht, 3584 CG, The Netherlands

    Holger Rehmann, Johan de Rooij & Johannes L. Bos

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Correspondence to Alfred Wittinghofer.

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Rehmann, H., Prakash, B., Wolf, E. et al. Structure and regulation of the cAMP-binding domains of Epac2. Nat Struct Mol Biol 10, 26–32 (2003). https://doi.org/10.1038/nsb878

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