Crystal Structure of PKG I:cGMP Complex Reveals a cGMP-Mediated Dimeric Interface that Facilitates cGMP-Induced Activation

• Published in: Structure (London) Vol. 24; no. 5; pp. 710 - 720
• Main Authors: Kim, Jeong Joo, Lorenz, Robin, Arold, Stefan T., Reger, Albert S., Sankaran, Banumathi, Casteel, Darren E., Herberg, Friedrich W., Kim, Choel
• Format: Journal Article
• Language: English
• Published: United States Elsevier Ltd 03-05-2016; Elsevier
• Subjects: 60 APPLIED LIFE SCIENCES; allosteric activation; BASIC BIOLOGICAL SCIENCES; Binding Sites; cGMP-dependent protein kinase; crystal structure; Crystallography, X-Ray; Cyclic GMP - chemistry; Cyclic GMP - metabolism; Cyclic GMP-Dependent Protein Kinase Type I - chemistry; Cyclic GMP-Dependent Protein Kinase Type I - metabolism; cyclic nucleotide-binding domain; Humans; Molecular Docking Simulation; Molecular Dynamics Simulation; NO-cGMP signaling; Protein Binding; Protein Multimerization; second messengers; small-angle X-ray scattering; cGMP-dependent protein kinase; second messengers; cyclic nucleotide-binding domain; crystal structure; allosteric activation; NO-cGMP signaling; small-angle X-ray scattering
• ISSN: 0969-2126; 1878-4186
• DOI: 10.1016/j.str.2016.03.009

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.
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•Structure of monomeric PKG I R reveals a new dimeric interface mediated by cGMP•Mutagenesis of the key interface residues reduces cGMP binding and activation•SAXS analysis of the PKG I R dimer supports the cGMP-mediated dimer model•The dimeric interface may acts as a “safety lock” to ensure kinase activation
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.