Misoprostol is a life-saving drug in many developing countries for women at risk of post-partum hemorrhaging owing to its affordability, stability, ease of administration and clinical efficacy. However, misoprostol lacks receptor and tissue selectivities, and thus its use is accompanied by a number of serious side effects. The development of pharmacological agents combining the advantages of misoprostol with improved selectivity is hindered by the absence of atomic details of misoprostol action in labor induction. Here, we present the 2.5 Å resolution crystal structure of misoprostol free-acid form bound to the myometrium labor-inducing prostaglandin E2 receptor 3 (EP3). The active state structure reveals a completely enclosed binding pocket containing a structured water molecule that coordinates misoprostol's ring structure. Modeling of selective agonists in the EP3 structure reveals rationales for selectivity. These findings will provide the basis for the next generation of uterotonic drugs that will be suitable for administration in low resource settings.

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Data availability

The misoprostol-FA EP3 receptor complex structure coordinates and structure factors are available via the Protein Data Bank (PDB) accession code 6M9T.

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This research was supported by NIH R35 GM127086 (V.C.), R21 DA042298 (W.L.), R01 GM124152 (W.L.), the STC Program of the National Science Foundation through BioXFEL (No. 1231306) (U.W. and W.L.), the Russian Science Foundation (project no. 16-14-10273), and the GPCR Consortium. M.A. was supported by a Canadian Institute of Health and Research (CIHR) Postdoctoral Fellowship Award. C.G. acknowledges the Panofsky Fellowship from SLAC National Accelerator Laboratory and Stanford University for financial support. P.P. and V.K. acknowledge the Russian Foundation for Basic Research (RFBR No.18-34-00990). Parts of this research were carried out at the LCLS, a National User Facility operated by Stanford University on behalf of the US Department of Energy and is supported by the US Department of Energy, Office of Science, Office of Basic Energy Sciences under contract no. DE-AC0276SF00515, and at the GM/CA CAT of the Argonne Photon Source, Argonne National Laboratory. We thank A. Walker for assistance in manuscript preparation; M. Chu, K. Villiers and C. Hanson for baculovirus expression and mammalian cell culture, and N. Sawyer for helpful suggestions. We are grateful to F. Badeaux and E. Audet-Badeaux for their encouragement and support.

Author information

Author notes

    • Petr Popov

    Present address: Koltech Institute of Science & Technology, Moscow, Russia


  1. Departments of Biological Sciences and Chemistry, Bridge Institute, Michelson Center for Convergent Bioscience, University of Southern California, Los Angeles, CA, USA

    • Martin Audet
    • , Kate L. White
    • , Barbara Zarzycka
    • , Gye Won Han
    • , Petr Popov
    • , Jeffrey Velasquez
    • , David Manahan
    • , Vsevolod Katritch
    • , Vadim Cherezov
    •  & Raymond C. Stevens
  2. Domain Therapeutics NA Inc., Montreal, Canada

    • Billy Breton
  3. iHuman Institute, ShanghaiTech University, Shanghai, China

    • Yan Lu
    •  & Wenqing Shui
  4. School of Life Science and Technology, ShanghaiTech University, Shanghai, China

    • Yan Lu
    •  & Wenqing Shui
  5. Biosciences Division, SLAC National Accelerator Laboratory, Menlo Park, CA, USA

    • Cornelius Gati
  6. Department of Structural Biology, School of Medicine, Stanford University, Palo Alto, CA, USA

    • Cornelius Gati
  7. Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, CA, USA

    • Alexander Batyuk
  8. Moscow Institute of Physics & Technology, Dolgoprudn, Russia

    • Petr Popov
    • , Vsevolod Katritch
    •  & Vadim Cherezov
  9. Biodesign Center for Applied Structural Discovery, Biodesign Institute, School of Molecular Sciences, Arizona State University, Tempe, AZ, USA

    • Hao Hu
    • , Uwe Weierstall
    •  & Wei Liu
  10. GPCR Consortium, San Marcos, CA, USA

    • Michael A. Hanson


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M.A. designed the study, crystallized the EP3 receptor, prepared samples for data collection, collected the data for XFEL and synchrotron, and solved and refined the structure. K.L.W. and M.A. performed the binding assays. B.B. performed the signaling assays. B.Z. and V.K. performed ligand docking and selectivity analysis. Y.L. and W.S. performed mass spectrometry. J.V. and D.M. performed molecular biology. P.P. suggested the mutation. C.G. processed the crystallographic XFEL data. A.B. helped with the XFEL data collection. W.L. helped with sample preparation for XFEL data collection. H.H. and U.W. operated the sample injector during XFEL data collection. G.W.H. solved and refined the structure. V.C. supervised XFEL data collection and processing. M.A.H., V.K., and R.C.S. supervised the project. All authors wrote the manuscript.

Competing interests

B.B is an employee of Domain Therapeutics NA, a company focused on GPCR drug discovery that sells and licenses the cell signaling kit used in this study. All other authors declare no competing interests.

Corresponding author

Correspondence to Raymond C. Stevens.

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