Notes on the Serpentines

Crystal Structure of the Active State Complex with Nucleotide-Free G-Protein Trimer

It is truly an astonishing moment seeing something dying to see it for sometime, as well as witnessing a magnificent achievement. For a first time, the crystal structure of G-protein coupled receptor ternary complex, obtained in a combined efforts between the groups in the USA, Denmark and Ireland, has been revealed - making another milestone which has finally been fixed in the history of receptor pharmacology.

The study published in Nature is:

Crystal structure of the β2 adrenergic receptor-Gs protein complex
Søren G. F. Rasmussen 1,2, Brian T. DeVree 3, Yaozhong Zou 1, Andrew C. Kruse 1, Ka Young Chung 1, Tong Sun Kobilka 1, Foon Sun Thian 1, Pil Seok Chae 4, Els Pardon 5,6, Diane Calinski 3, Jesper M. Mathiesen 1, Syed T. A. Shah 7, Joseph A. Lyons 7, Martin Caffrey 7, Samuel H. Gellman 4, Jan Steyaert 5,6, Georgios Skiniotis 8, William I. Weis 1,9, Roger K. Sunahara 3 & Brian K. Kobilka 1.
1. Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, California 94305, USA. 2. Department of Neuroscience and Pharmacology, The Panum Institute, University of Copenhagen, 2200 Copenhagen N, Denmark. 3. Department of Pharmacology, University of Michigan Medical School, Ann Arbor, Michigan 48109, USA. 4. Department of Chemistry, University of Wisconsin, Madison, Wisconsin 53706, USA. 5. Department of Molecular and Cellular Interactions, Vlaams Instituut voor Biotechnologie (VIB), Vrije Universiteit Brussel, B-1050 Brussel, Belgium. 6. Structural Biology Brussels, Vrije Universiteit Brussel, B-1050 Brussels, Belgium. 7. Membrane Structural and Functional Biology Group, Schools of Medicine and Biochemistry & Immunology, Trinity College, Dublin 2, Ireland. 8. Life Sciences Institute and Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA. 9. Department of Structural Biology, Stanford University School of Medicine, Stanford, California 94305, USA.

Many congratulations to the groups above for their successes in obtaining this, and thank you all the above for making it possible to see it.

Brief Summary

PDB file: 3SN6

Method: x-ray diffraction

Resolution: 3.20 angstrom

The complex comprising five polymers:
1. Bovine Gαs short isoform (380 amino acids)
2. Rat Gβ1 GI/GS/GT (351 a.a.)
3. Bovine Gγ2 GI/GS/GT (68 a.a.)
4. Enterobacteriophage T4 Lysozme--Human Beta-2 Adrenoceptor chimera (514 a.a.)
5. Llama Camelid antibody VHH fragment (138 a.a.) i.e. nanobody Nb35 Gs-binding nanobody Nb35 stabilised the β2AR-Gs complex.

Ligand: the receptor has an agonist BI-167107 bound.

Their journal article published in Nature beautifully illustrates the outward movement of TMs, notably of TM6 (14 angstrom) and to a less degree of TM5 in overlaid crystal structures of the newly obtained active β2AR and the previously obtained inactive counterpart (figure 3 in the original article).

The article reveals the interactions between the receptor and Gs in substantial detail. TM3, TM5 and ICL2 were shown to participate mainly (figure 4 in the article).

They have also compared conformational changes in Gs regarding GTPγS binding, revealing a rotated displacement (6 angstrom) of α5 helix of Gs from nearby ICL2 towards the core of the 7TMs upon GTPγS release (figure 5 in the article).

The article insightfully closes with a proposed sequence of the receptor-Gs complex formation (figure 6 in the article).

Delightedly, there are more information technically relevant in detail to come in following two publications (Westfield et al.; Chung et al. submitted).

Here are some pictures:

The pentameric complex containing T4 lysozyme-human β2AR chimera (yellow), bovine Gs (blue), rat Gβ (cyan), bovine Gγ2 (green) and llama nanobody 35 (red).

The side view facing to TM3-ICL2 and Gs.