Cyclic guanosine monophosphate (cGMP)-dependent protein kinase (PKG) is a key regulator of smooth muscle and vascular tone and represents an important drug target for treating hypertensive diseases and erectile dysfunction. Despite its importance, its activation mechanism is not fully understood. To understand the activation mechanism, we determined a 2.5 Å crystal structure of the PKG I regulatory (R) domain bound with cGMP, which represents the activated state. Although we used a monomeric domain for crystallization, the structure reveals that two R domains form a symmetric dimer where the cGMP bound at high-affinity pockets provide critical dimeric contacts. Small-angle X-ray scattering and mutagenesis support this dimer model, suggesting that the dimer interface modulates kinase activation. Finally, structural comparison with the homologous cyclic AMP-dependent protein kinase reveals that PKG is drastically different from protein kinase A in its active conformation, suggesting a novel activation mechanism for PKG. Kim et al. obtain the first crystal structure of the PKG I R domain bound with cGMP representing its activated state. It reveals a symmetric R dimer where cGMP molecules provide dimeric contacts. This R-R interaction prevents the high-affinity inhibitory interaction between R-C domain and sustains activation. © 2016 Elsevier Ltd.
|Original language||English (US)|
|Number of pages||11|
|State||Published - Apr 9 2016|
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledgements: We thank Dr. Gilbert Y. Huang (M.D. Anderson Cancer Center) and the members of Kim's laboratory for critical reading of the manuscript and E. Franz (University of Kassel) for technical support. We specially thank R. Sanishvili, M. Becker, and C. Ogata (GM/CA@APS) for their kind assistance with data collection during the APS-CCP4 summer school in 2012. C.K. was funded by the NIH grants R01 GM090161 and R21 HL111953. The CCP4 school was funded partly by the NCI (Y1-CO-1020), the NIGMS (Y1-GM-1104), a grant from CCP4, and the STFC in the UK. Research by S.T.A. reported in this publication was supported by funding from King Abdullah University of Science and Technology (KAUST). F.W.H. was supported by the Federal Ministry of Education and Research Project NO PAIN (FKZ 0316177F) and the European Union (EU) FP7 collaborative project AFFINOMICS (contract no. 241481). The Berkeley Center for Structural Biology is supported in part by the NIH, the National Institute of General Medical Sciences, and the Howard Hughes Medical Institute. The Advanced Light Source is supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under contract no. DE-AC02-05CH11231. The SIBYLS beamline (ALS) is supported in part by US DOE program Integrated Diffraction Analysis Technologies (IDAT) and the NIH project MINOS (R01 GM105404).