Frog-skin nerve peptide (Rohdei-Litorin): mirrors a human brain signaling molecule
A peptide from South American tree frog skin that switches on the same receptor as a human brain hormone; used only as a lab research tool to study pain, dopamine, and cancer.
- Class
- Amphibian neuropeptide (bombesin-litorin family)
- Best-supported effect
- Receptor binding affinity to rat urinary bladder receptors in assay systems
- Main caveat
- No animal or human efficacy data identified; structure and sequence only
A researcher, an agent, or an algorithm wrote down the sequence and picked a target to hit.
An AI model like OpenFold3 or AlphaFold built a 3D structure and scored how well it fits the binding site.
A second contributor repeated the computation on their own hardware and the scores matched.
A chemistry service or a researcher ordered the sequence, it was manufactured, and mass spectrometry confirmed the right molecule was produced.
A binding or activity measurement confirmed that it actually does what the computer predicted — or didn't.
What this is
Rohdei-litorin is a small peptide isolated from the skin of the South American tree frog Phyllomedusa rohdei. It belongs to the bombesin/litorin peptide family — a group of signaling molecules first discovered in amphibian skin that have close structural and functional counterparts in mammals. Rohdei-litorin is the amphibian equivalent of neuromedin B (NMB), a neuropeptide found in the human pituitary gland and brain; the two peptides share an identical eight-residue C-terminal sequence (Barra and colleagues, FEBS Letters, 1985). The stored sequence (LWATGHFM) represents those eight residues; the full native peptide additionally carries a pyroglutamic acid (pGlu) cap at the N-terminus and a C-terminal amide (-NH₂), neither of which are encoded in the raw sequence shown.
History
Rohdei-litorin was first isolated and sequenced by Barra and colleagues at the University of Rome and published in FEBS Letters in 1985. Its discovery came during a broader effort by Vittorio Erspamer's group to catalog the extraordinary diversity of bioactive peptides present in Phyllomedusa frog skins — a project that had already yielded dermorphin, phyllocaerulein, and several other pharmacologically active compounds. The finding that rohdei-litorin shared its entire C-terminal octapeptide with neuromedin B — a mammalian neuropeptide identified from porcine spinal cord — established the "amphibian counterpart" relationship that has since shaped how researchers use litorin-family peptides to probe NMB receptor biology (Barra and colleagues, 1985).
What it does
Rohdei-litorin, like its mammalian counterpart neuromedin B, activates bombesin-type receptors — G protein-coupled receptors that regulate smooth muscle contraction, hormone secretion, and signaling in the brain. Among bombesin-family peptides, rohdei-litorin showed greater affinity for rat urinary bladder receptors than other family members tested at the time of its discovery (Barra and colleagues, 1985), consistent with the profile of the neuromedin B receptor (BB1 / NMBR). The neuromedin B receptor, which rohdei-litorin's C-terminal sequence shares with the endogenous mammalian ligand, governs multiple physiological circuits: it acts as a paracrine inhibitor of TSH release in the pituitary–thyroid axis, contributes to itch signal relay in spinal cord circuits (operating through NMBR-positive neurons distinct from GRP/GRPR pathways), and mediates fear and anxiety responses in the amygdala (Gonzalez and colleagues, 2008; Wan and colleagues, 2017).
Evidence
- Human: No human clinical trials for rohdei-litorin itself are registered on ClinicalTrials.gov. The receptor it characterizes — the neuromedin B receptor — has been studied in humans primarily through receptor expression surveys in tumors and pituitary tissue.
- Animal: Receptor binding studies in rat urinary bladder demonstrated rohdei-litorin's greater affinity over other litorin-family members (Barra and colleagues, 1985). Neuromedin B receptor knockout mice developed by Oliveira and colleagues (2006) showed 18% elevation in baseline TSH and reduced T3, confirming the receptor's role in pituitary-thyroid regulation. Wan and colleagues (2017) demonstrated that NMB-specific spinal cord pathways relay histamine- and serotonin-induced itch independently of GRP/GRPR pathways.
- In vitro: Rohdei-litorin belongs to the litorin/ranatensin bombesin sub-family; pharmacological profiling across bombesin receptor subtypes by Uehara and colleagues (2011) showed that litorin-family peptides display relatively high affinity at the human NMB receptor (BB1) relative to the GRP receptor (BB2).
Known effects
- Smooth muscle contraction (bladder, GI tract) — Preclinical; litorin-family peptides stimulate contraction via bombesin receptors (Barra and colleagues, 1985; Jensen and colleagues, 2008)
- Pituitary–thyroid axis modulation — Preclinical (knockout model); NMB receptor signaling tonically inhibits TSH secretion (Oliveira and colleagues, 2006)
- Spinal itch transmission — Preclinical; NMB/NMBR relay histamine and serotonin pruritogenic signals in spinal cord lamina II (Wan and colleagues, 2017)
- Fear and anxiety modulation — Preclinical; NMB receptor activation in the central lateral amygdala reduces fear-potentiated startle (Gonzalez and colleagues, 2008)
- Satiety signaling — Preclinical; NMB/BB1-receptor contributes to satiety regulation via pathways distinct from those used by GRP/BB2 (Jensen and colleagues, 2008)
Mechanism
Rohdei-litorin's pharmacological activity derives from its C-terminal octapeptide (LWATGHFM, the sequence stored on this card), which is the shared pharmacophore with neuromedin B (NMB). This region is the minimum sequence required for high-affinity binding to the neuromedin B receptor (NMBR / BB1), a class A GPCR. Upon NMBR activation, downstream Gαq/phospholipase C signaling raises intracellular calcium and activates protein kinase C, mediating smooth muscle contraction and hormone secretion. The selectivity of the litorin/ranatensin subfamily for the NMB receptor over the GRP receptor (BB2) is conferred by the tetrapeptide motif -Gly-His-Phe-Met-NH₂ at the extreme C-terminus — rohdei-litorin carries this motif intact. High-affinity NMB binding at the NMBR is structurally determined by residues in transmembrane domain V of the receptor (Uehara and colleagues, 2011). The full native peptide has a pyroglutamic acid N-cap (not stored in the raw sequence) that protects the peptide from N-terminal exopeptidases and is characteristic of several amphibian skin peptide families.
Safety signals
No safety or toxicological data for rohdei-litorin in humans has been published. As a research peptide used to characterize bombesin receptor pharmacology, it has not been evaluated in clinical studies.
Related peptides
- Neuromedin B — the endogenous mammalian neuropeptide sharing the identical C-terminal octapeptide as rohdei-litorin; the primary endogenous ligand of the NMBR/BB1 receptor
- Litorin — the closely related amphibian bombesin-family peptide from Hyla arborea skin; differs at residues N-terminal to the shared C-terminal core
- Bombesin — the founding member of the bombesin/GRP/NMB peptide family, isolated from Bombina bombina skin; high affinity for both BB1 and BB2 receptors
▸full evidence table2 metrics
| metric | value | tool |
|---|---|---|
| ipTM | 0.8892742991447449 | boltz-2 |
| ranking score | 0.7642424702644348 | boltz-2 |
▸structural qualityopenfold3
| metric | value | note |
|---|---|---|
| gpde | 1.014 | global PDE — lower = better |
| disorder | NaN | fraction disordered |
▸3-letter notation
▸recipeboltz-2 1.0
| parameter | value |
|---|---|
| model | boltz-2 1.0 |
| weights | — |
| hardware | nvidia_nim_api |
| mlx version | — |
| python | — |
| random seed | — |
| msa strategy | none |
| diffusion samples | 1 |
| runtime | — |
| predicted by | mlx@peptide |
| predicted at | 2026-04-24 |
▸citationbibtex
@peptide{pep10622,
sequence = {LWATGHFM},
target = {ntsr1},
author = {peptidemodel},
year = {2026},
status = {synthesized}
}