IGF-1 middle fragment (positions 30: 41), small piece of the growth factor IGF-1
A short lab-made snippet copied from the middle of IGF-1, a natural growth-promoting protein. Used only as a research tool to study how IGF-1 works, not a medicine.
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.
Named peptide fragment — synthesized for research; ClinicalTrials.gov trials registered for parent compound or class
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Endogenous peptide fragment — receptor binding/activity established in published literature; CT.gov evidence
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What this is
IGF-I (30-41) is a short 12-amino-acid fragment (GYGSSSRRAPQT) corresponding to the "C domain" of human insulin-like growth factor 1 (IGF-1) — the connecting loop that sits between the B and A domains of the parent hormone. It is not the full hormone and does not engage the IGF-1 receptor the way intact IGF-1 does; it is the isolated middle stretch of IGF-1, studied as a synthetic peptide in its own right. The same 12-residue sequence appears verbatim inside the larger IGF-1 backbone (positions 30–41 of the mature hormone) and inside its IGF-1Ec splice variant ("mechano growth factor" precursor) as well (Mavrommatis 2013, ajpendo.00408.2013).
What it does
As an isolated peptide, the IGF-I C-domain fragment is studied for activity that is distinct from full-length IGF-1's mitogenic and growth-promoting actions. The synthetic 12-mer GYGSSSRRAPQT has been examined as a "C Domain peptide" in the context of suppressing inflammatory signalling and supporting recovery in models of colitis, where it has been associated with attenuation of TNF-α–driven inflammation (d5ra03731j). In the body, the same sequence — when embedded inside the intact IGF-1 hormone — participates in the receptor-binding fold that engages the IGF-1 receptor (IGF-1R), but as a free 12-mer it does not reproduce full IGF-1's metabolic or growth effects.
Mechanism
Full-length IGF-1 acts through the IGF-1 receptor, a transmembrane tyrosine kinase whose activation involves trans-phosphorylation of the activation loop in the kinase domain (Wu 2008). IGF-1R signalling is tightly regulated by receptor trafficking, β-arrestin recruitment and post-translational modification, with downstream cascades that integrate growth, survival and metabolic outputs (Girnita 2014). The C-domain of IGF-1 — the segment from which this 12-mer is taken — contributes to the receptor-binding surface within the intact hormone; the free GYGSSSRRAPQT peptide lacks the disulfide-bonded scaffold of intact IGF-1 (three disulfide bridges hold the A and B domains together in the full hormone) and therefore cannot recapitulate full IGF-1R agonism on its own. The IGF-1 system also includes a family of IGF-binding proteins (IGFBPs) that bind circulating IGF-1 and modulate its tissue availability — N-terminally truncated and engineered IGF-1 variants with low IGFBP affinity (des(1-3)IGF-I and LR3-IGF-I) have markedly different distribution and potency profiles than native IGF-1, which is one reason engineered IGF-1 analogs behave differently from the native hormone in vivo (Tomas 1993, Bastian 2000).
Evidence
- Human: No human clinical trials of the isolated IGF-I (30-41) peptide are documented in the sources gathered for this card. Human evidence in the dossier concerns the parent hormone IGF-1 and the broader GH/IGF-1 axis in pediatric growth hormone deficiency and aging (Soliman 2025, Fernández-Garza 2025).
- Animal: Animal evidence in the dossier addresses full-length IGF-1 and engineered IGF-1 variants rather than the 12-mer fragment specifically: IGF-1 and its IGFBP-resistant variants (des(1-3)IGF-I, LR3-IGF-I) restored growth in streptozotocin-diabetic rats without producing the full range of insulin's metabolic effects (Tomas 1993); LR3-IGF-I crossed an endothelial barrier model and reached wound fluid more readily than IGF-1, which is constrained by IGFBP binding (Bastian 2000); and IGF-1, IGF-2 and des(1-3)IGF-1 each reduced neuronal loss after hypoxic-ischemic brain injury in adult rats, with IGFBP modulation a likely contributor (Guan 1996).
- In vitro: A synthetic 12-mer matching this sequence ("C Domain peptide", GYGSSSRRAPQT) has been examined in inflammation/colitis-recovery contexts, with reported suppression of TNF-α–driven inflammatory signalling (d5ra03731j). Receptor-level mechanistic work has focused on the IGF-1 receptor itself rather than the C-domain peptide — including small-molecule inhibitor binding and the trans-phosphorylation behaviour of the IGF-1R activation loop (Wu 2008).
Related peptides
- Engineered IGF-1 variants — des(1-3)IGF-I (the N-terminally truncated form) and LR3-IGF-I (arginine substitution at residue 3 plus an N-terminal extension) are IGF-1 analogs with reduced IGFBP affinity and altered tissue distribution (Tomas 1993, Bastian 2000). These are different peptides — they retain the full IGF-1 fold; the card you are reading is the isolated C-domain 12-mer only.
- Full-length IGF-1 and IGF-1Ec — IGF-I (30-41) is a substring of both the mature 70-residue IGF-1 hormone and the IGF-1Ec splice variant (mechano growth factor precursor), corresponding to the C-domain loop that connects the B and A domains (ajpendo.00408.2013).
Research directions for this peptide, selected from the current sources — hypotheses you can explore and model. None of it is proven yet; tap any one to see the full thinking.
Does this small piece of IGF-1 bind to a different, undiscovered receptor instead of the one the full hormone uses?
If the fragment acts through a separate receptor, it could be developed as an anti-inflammatory drug that avoids the cancer-promoting risk linked to stimulating IGF-1R. That would matter for patients with inflammatory bowel disease who cannot safely use full-length growth factor therapies.
Could this fragment protect the intestinal lining in bowel disease without the cancer-risk side effects of the full hormone?
Patients with Crohn's disease or ulcerative colitis need therapies that heal the gut without raising cancer risk. If this fragment achieves one without the other, it could be a safer long-term option than full-length IGF-1 or current immunosuppressants.
Does this fragment reduce gut inflammation by directly interfering with the TNF-alpha signaling chain rather than through the growth-factor receptor?
If true, this peptide could become a new, body-derived drug for inflammatory bowel disease that works differently from existing TNF-blocking antibodies, potentially with fewer side effects because it comes from a human protein sequence.
▸full evidence table2 metrics
| metric | value | tool |
|---|---|---|
| ipTM | 0.2013091892004013 | boltz-2 |
| ranking score | 0.44712695479393005 | boltz-2 |
▸3-letter notation
▸recipeboltz-2 2.2.1
| parameter | value |
|---|---|
| model | boltz-2 2.2.1 |
| weights | — |
| hardware | vast_v100_32gb |
| mlx version | — |
| python | — |
| random seed | 1 |
| msa strategy | colabfold_local |
| runtime | — |
| predicted by | — |
| predicted at | 2026-05-22 |
▸citationbibtex
@peptide{pep10734,
sequence = {GYGSSSRRAPQT},
target = {igf-1r},
author = {peptidemodel},
year = {2026},
status = {bioassayed}
}