The Melanocortin Receptor Family
The melanocortin receptor family has five named subtypes, MC1 through MC5. The number identifies the receptor a study examined. To interpret a reported effect, read the receptor name together with the ligand structure, species and response that the researchers measured. [1]
Read the nomenclature carefully
In the IUPHAR nomenclature, MC2 is the adrenocorticotropic hormone (ACTH) receptor. The similarly written MT1 and MT2 are names in a separate family, the melatonin receptors. The commercial abbreviations MT-1 and MT-2 on a vial should be checked against its specification before drawing any molecular or receptor conclusion. [1]
| Label | What it identifies |
|---|---|
| MC1, MC2, MC3, MC4, MC5 | Receptor subtypes |
| ACTH or alpha-MSH | Named endogenous peptide ligands |
| A modified melanocortin analogue | A specific structure that must be defined |
| MT-1 or MT-2 on a supplier record | An abbreviation requiring supplier identity confirmation |
How one modified ligand can act differently at different receptors
Hruby and colleagues varied the aromatic amino acid at position 7 in a series of cyclic melanotropin analogues. One naphthylalanine-containing analogue acted as an agonist at human MC1 in a cloned-receptor assay, while showing antagonist activity with a partial agonist component at human MC3 and MC4. A single label for the entire receptor family would lose those differences. [2]
Keep the exact analogue beside the finding. Changing one residue or moving from a frog-skin assay to a cloned human receptor can change what the readout represents. These experiments examined defined structures and assay systems.
Extract the evidence before comparing ligands
When comparing two papers, record the sequence and modification, receptor subtype, species, experimental system and endpoint. A binding result estimates interaction with a target. A functional assay asks whether the ligand changes the measured response. Mark any untested receptor explicitly.
Use receptor agonists and selectivity for the terminology. The alpha-MSH and KPV guide explains why a shared sequence fragment alone cannot establish the same activity for KPV 10 mg.
Catalogue relationship remains unresolved
Knockout Labs lists MT-1 10 mg and MT-2 10 mg. Their exact molecular identities and classification remain unresolved. For either presentation, ask for the sequence or structure, modifications and lot-linked specification before selecting a receptor study as a comparator.
Explore the related evidence
| Resource | Why open it |
|---|---|
| KPV | Check KPV sequence, terminal chemistry and analytical scope. |
| Guides & Resources | Choose another scientific, analytical or procurement guide. |
Sources and scope
- Alexander and colleagues ยท The Concise Guide to Pharmacology 2025/26, G protein-coupled receptors The melanocortin and melatonin sections give the distinct receptor nomenclatures. See the melanocortin table on page S97.
- Hruby et al. (1995). Cyclic lactam alpha-melanotropin analogues and receptor selectivity. The authors compared defined cyclic analogues in several receptor systems and reported mixed functional profiles for some substitutions.