9K3K image
Deposition Date 2024-10-19
Release Date 2025-08-06
Last Version Date 2025-08-06
Entry Detail
PDB ID:
9K3K
Keywords:
MEMBRANE PROTEIN
Title:
Cryo-EM structure of the unliganded human melanocortin receptor 4 (MC4R)-Gs complex
Biological Source:
Source Organism:
Homo sapiens (Taxon ID: 9606)
synthetic construct (Taxon ID: 32630)
Bos taurus (Taxon ID: 9913)
Host Organism:
Spodoptera frugiperda
Method Details:
Experimental Method:
ELECTRON MICROSCOPY
Resolution:
3.12 Å
Aggregation State:
PARTICLE
Reconstruction Method:
SINGLE PARTICLE
9K3K validation report
Macromolecular Entities
Protein Blast
Polymer Type:polypeptide(L)
Molecule:Guanine nucleotide-binding protein G(i) subunit alpha-1,Guanine nucleotide-binding protein G(s) subunit alpha isoforms short
Gene (Uniprot):GNAS, GNAI1
Mutagens:G49D,E50N,L63Y,G226A,A249D,S252D,L272D,A366S,I372A,V375I
Chain IDs:B (auth: A)
Chain Length:361
Number of Molecules:1
Biological Source:Homo sapiens
UniProt ID:P63092,P63096 Pfam ID:PF00503
Structures with similar UniProt ID
Protein Blast
Polymer Type:polypeptide(L)
Molecule:Guanine nucleotide-binding protein G(I)/G(S)/G(T) subunit beta-1,Guanine nucleotide-binding protein G(I)/G(S)/G(T) subunit beta-1,Guanine nucleotide-binding protein G(I)/G(S)/G(T) subunit beta-1,HiBiT
Gene (Uniprot):GNB1
Chain IDs:C (auth: B)
Chain Length:371
Number of Molecules:1
Biological Source:Homo sapiens, synthetic construct
UniProt ID:P62873 Pfam ID:PF00400
Structures with similar UniProt ID
Protein Blast
Polymer Type:polypeptide(L)
Molecule:Guanine nucleotide-binding protein G(I)/G(S)/G(O) subunit gamma-2
Gene (Uniprot):GNG2
Chain IDs:D (auth: G)
Chain Length:71
Number of Molecules:1
Biological Source:Bos taurus
UniProt ID:P63212 Pfam ID:PF00631
Polymer Type:polypeptide(L)
Molecule:Nb35
Chain IDs:E (auth: N)
Chain Length:160
Number of Molecules:1
Biological Source:synthetic construct
Structures with similar UniProt ID
Protein Blast
Polymer Type:polypeptide(L)
Molecule:Melanocortin receptor 4,Melanocortin receptor 4,Melanocortin receptor 4,LgBiT subunit
Gene (Uniprot):MC4R
Chain IDs:A (auth: R)
Chain Length:505
Number of Molecules:1
Biological Source:Homo sapiens, synthetic construct
UniProt ID:P32245 Pfam ID:PF00001
Polymer Type:polypeptide(L)
Molecule:scFv16
Chain IDs:F (auth: S)
Chain Length:285
Number of Molecules:1
Biological Source:synthetic construct
Ligand Molecules
NA
Primary Citation
Structural basis for the constitutive activity of the melanocortin receptor family.
Structure 33 1074 1087.e5 (2025)
PMID: 40157361 DOI: 10.1016/j.str.2025.03.004

Abstact

The constitutive activity of melanocortin receptors (MCRs) is integral to several physiological processes. The unliganded cryo-electron microscopy structures of MC1R, MC2R, MC3R, MC4R, and MC5R in complex with Gs proteins determined at global resolutions of 2.98 Å, 3.01 Å, 2.75 Å, 3.12 Å, and 2.86 Å, respectively, revealed that their binding poses and interactions with Gs are similar to those of agonist-bound MCRs. The extracellular regions of the transmembrane helices (TMs) exhibit distinct conformational rearrangements, characterized by varying shifts of TM3 and outward displacements of TM4. These variations represent unique structural features of constitutively activated MCRs. Unassigned electron densities were observed within the orthosteric pockets where extensive interactions with cognate ligands occur. In addition, zinc ions, but not calcium, positively regulated MC4R activity in a dose-dependent manner. Our findings provide valuable insights into the molecular mechanisms underlying MCR basal activity and highlight the role of divalent ions in receptor activation.

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Primary Citation of related structures
9K3K