Structural Research of G Protein-coupled Receptors (GPCRs) Class A

G protein-coupled receptors (GPCRs) are integral membrane proteins that play essential roles in cellular signaling and communication. Among the GPCRs, class A receptors are the largest and most extensively studied subgroup, with significant implications in various physiological processes, including neurotransmission, hormone regulation, and immune responses. In recent decades, structural research on class A GPCRs has significantly advanced, shedding light on their activation mechanisms and providing insights into the development of novel therapeutics.

Class A GPCRs are characterized by their seven-transmembrane helices and their activation through G protein coupling. These receptors are of great interest to researchers due to their involvement in a wide range of physiological functions and their potential as drug targets. Early research on GPCRs mainly relied on X-ray crystallography, which led to landmark discoveries, such as the first high-resolution structure of a GPCR, rhodopsin, in 2000.

Over the past two decades, the advent of cryo-electron microscopy (cryo-EM) has revolutionized structural biology, allowing the visualization of GPCRs at near-atomic resolution. The latest cryo-EM structures of GPR119 (a cannabinoid receptor-like class A GPCR) and its interactions with agonists provide significant revelations regarding its activation and signaling mechanisms, thereby contributing to the advancement of innovative therapeutic strategies.

Figure 1. Overall cryo-EM structures of the GPR119-Gs heterotrimer complexes. (Qian Y, et al., 2022)

Protein	Organism	Method	Resolution	PDB Entry ID
Rhodopsin in ligand-free state (opsin)	Bos taurus	X-ray diffraction	2.65 Å	4J4Q
Rhodopsin in ligand-free state (opsin)	Bos taurus	X-ray diffraction	2.29 Å	4X1H
Rhodopsin in ligand-free state (opsin) in complex with ArrFL-1	Bos taurus	X-ray diffraction	2.75 Å	4PXF
Rhodopsin, N2C/D282C stabilized opsin bound to RS01 (expressed in HEK293S cells)	Bos taurus	X-ray diffraction	2.36 Å	6FK6
Rhodopsin-Gαi-βγ complex (expressed in HEK293 cells)	Bos taurus	Cryo-EM single particle analysis	4.38 Å	6QNO
Rhodopsin-Transducin Complex (expressed in Escherichia coli)	Bos taurus	Cryo-EM single particle analysis	3.90 Å	6OY9
Visual Signaling Complex between Transducin and Phosphodiesterase 6 (expressed in Escherichia coli)	Bos taurus	Cryo-EM single particle analysis	3.20 Å	7JSN
Rhodopsin (native dimer) in nanodiscs	Bos taurus	Cryo-EM single particle analysis	4.50 Å	6OFJ
Rhodopsin in complex with rhodopsin kinase (GRK1) (expressed in Spodoptera frugiperda)	Bos taurus	Cryo-EM single particle analysis	7.00 Å	7MT9
Bovine rhodopsin in Lipidic Cubic Phase (SACLA)	Bos taurus	X-ray diffraction	1.80 Å	7ZBC
Human rhodopsin with bound mouse visual arrestin (expressed in HEK293S cells)	Homo sapiens	X-ray diffraction	3.30 Å	4ZWJ
Human rhodopsin with bound inhibitory G protein (Gi) (expressed in Sf9 cells)	Homo sapiens	Cryo-EM single particle analysis	4.50 Å	6CMO
Jumping Spider Rhodopsin-1 bound to 9-cis retinal (expressed in HEK293 cells)	Hasarius adansoni	X-ray diffraction	2.15 Å	6I9K
GPR17-Gi complex (expressed in Spodoptera frugiperda)	Homo sapiens	Cryo-EM single particle analysis	3.02 Å	7Y89
Gi bound orphan GPR20 in ligand-free state (expressed in Spodoptera frugiperda)	Homo sapiens	Cryo-EM single particle analysis	3.14 Å	8HS3
GPR21-Gs complex (expressed in Spodoptera frugiperda)	Homo sapiens	Cryo-EM single particle analysis	2.91 Å	8HMV
GPR52 ligand free form with flavodoxin fusion (expressed in Spodoptera frugiperda)	Homo sapiens	X-ray diffraction	2.90 Å	6LI1
Orphan GPR88 class A receptor - Gi1 complex, apo form (expressed in Spodoptera frugiperda)	Homo sapiens	Cryo-EM single particle analysis	3.00 Å	7WZ4
GPR119-Gs-LPC complex (expressed in Trichoplusia ni)	Homo sapiens	Cryo-EM single particle analysis	3.10 Å	7XZ5
GPR119-Gs Complex with small molecule agonist AR231453 (expressed in Trichoplusia ni)	Homo sapiens	Cryo-EM single particle analysis	2.87 Å	7WCN
Orphan GPCR in complex with Gi (expressed in Spodoptera frugiperda)	Homo sapiens	Cryo-EM single particle analysis	3.20 Å	7VUG
LPS-bound GPR174 in complex with Gs protein (expressed in Spodoptera frugiperda)	Homo sapiens	Cryo-EM single particle analysis	2.76 Å	7XV3
GSK682753A-bound EBI2/GPR183 (expressed in Spodoptera frugiperda)	Homo sapiens	Cryo-EM single particle analysis	2.98 Å	7TUY
OX1 orexin receptor with bound suvorexant (expressed in Spodoptera frugiperda)	Homo sapiens	X-ray diffraction	2.75 Å	4ZJ8
Orexin-1 receptor in complex with suvorexant (expressed in Spodoptera frugiperda)	Homo sapiens	X-ray diffraction	2.26 Å	6TO7
OX1 orexin receptor with bound subtype-selective antagonist (expressed in Spodoptera frugiperda)	Homo sapiens	X-ray diffraction	3.50 Å	6V9S
OX2 orexin receptor with bound suvorexant (expressed in Spodoptera frugiperda)	Homo sapiens	X-ray diffraction	2.50 Å	4S0V
OX2 orexin receptor in complex with suvorexant (expressed in Spodoptera frugiperda)	Homo sapiens	X-ray diffraction	2.74 Å	6TPJ
OX2 orexin receptor with bound antagonist EMPA (expressed in Sf9 cells)	Homo sapiens	X-ray diffraction	1.96 Å	5WQC
OX2 orexin receptor in complex with G protein and natural peptide-agonist Orexin B (OxB) (expressed in Trichoplusia ni)	Homo sapiens	Cryo-EM single particle analysis	3.20 Å	7L1U
OX2 orexin receptor in complex with Gi protein and TAK-925 (expressed in Spodoptera frugiperda)	Homo sapiens	Cryo-EM single particle analysis	3.17 Å	7SQO
OX2 orexin receptor with bound lemborexant (expressed in Spodoptera frugiperda)	Homo sapiens	X-ray diffraction	2.89 Å	7XRR
C5a anaphylatoxin chemotactic receptor 1 (C5aR) in complex with NDT9513727 (expressed in Spodoptera frugiperda)	Homo sapiens	X-ray diffraction	2.70 Å	5O9H
C5a anaphylatoxin chemotactic receptor 1 (C5aR) in complex with orthosteric antagonist PMX53 and allosteric antagonist NDT9513727 (expressed in Spodoptera frugiperda)	Homo sapiens	X-ray diffraction	2.90 Å	6C1Q
α1B-adrenergic receptor in complex with inverse agonist (+)-cyclazosin (expressed in Escherichia coli)	Homo sapiens	X-ray diffraction	2.87 Å	7B6W
alpha2A adrenergic receptor in complex with an antagonist RSC (expressed in Spodoptera frugiperda)	Homo sapiens	X-ray diffraction	2.70 Å	6KUX
alpha2A adrenergic receptor GoA signaling complex bound to a G protein biased agonist (expressed in Spodoptera frugiperda)	Homo sapiens	Cryo-EM single particle analysis	3.47 Å	7W6P
alpha2BAR-GoA complex (expressed in Sf9 cells)	Homo sapiens	Cryo-EM single particle analysis	2.90 Å	6K41
alpha2C adrenergic G protein-coupled receptor (expressed in Spodoptera frugiperda)	Homo sapiens	X-ray diffraction	2.80 Å	6KUW

Table 1. Structural research of class-A GPCRs.

Creative Biostructure offers comprehensive structural analysis services for class A GPCRs, tailored to meet the specific needs of researchers and pharmaceutical companies. Our multidisciplinary approach combines cryo-electron microscopy (cryo-EM), X-ray crystallography, and computational modeling to provide a holistic understanding of GPCR structures and their interactions with ligands and G proteins.

Researchers and pharmaceutical companies seeking to gain a deeper understanding of GPCRs and harness this knowledge to develop novel therapies are encouraged to collaborate with Creative Biostructure. Our state-of-the-art facilities, experienced team, and track record of successful structural studies make us a reliable partner in advancing the field of GPCR research. Contact us to discover how our cutting-edge capabilities can empower your research and drive you closer to achieving your scientific goals.

References

Chen G, et al. Activation and allosteric regulation of the orphan GPR88-Gi1 signaling complex. Nature Communications. 2022, 13(1): 2375.
Qian Y, et al. Activation and signaling mechanism revealed by GPR119-Gs complex structures. Nature Communications. 2022, 13(1): 7033.