Gastrin-34 [1-8]: lab tool for studying gut satiety signals
A short fragment of gastrin, a stomach hormone, used in lab research to study how the gut signals fullness and triggers gallbladder contraction. Used only as a lab research tool.
- Class
- Endogenous gastrin fragment
- Status
- No approved therapeutic status identified
- Main caveat
- Source is a catalog entry with sequence notation and one molecular-cloning reference; no bioactivity, animal, or human evidence is attached.
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
Gastrin-34 [1-8] is a short peptide corresponding to the first eight residues of "big gastrin" (gastrin-34), the 34-amino-acid form of the gastrin hormone produced by G-cells in the stomach and duodenum. The stored sequence LGPQGPP represents positions 2–8 of the full gastrin-34 chain; position 1 is a pyroglutamic acid (pGlu, a cyclized form of glutamic acid) that cannot be encoded as a standard single-letter amino acid. This fragment spans the proline-rich N-terminal arm that is unique to gastrin-34 and absent from the shorter gastrin-17, making it useful as an immunological and structural research tool for studying gastrin processing and for raising antisera that can distinguish the two major forms.
History
Gastrin was identified in the early twentieth century as the hormone driving gastric acid secretion, but its multiple molecular forms were not resolved until decades later. The larger circulating form, gastrin-34 ("big gastrin"), was isolated alongside the well-known gastrin-17 ("little gastrin"). The complete molecular basis of the human gastrin precursor was established in 1983, when Boel and colleagues cloned human gastrin cDNA from a gastrinoma library and deduced the full 101-amino-acid preprogastrin sequence, showing that both G34 and G17 are derived from the same gene with their boundaries defined by pairs of basic amino acid residues — and that an internal sequence duplication within the gene suggests gastrin evolved from an ancient ancestral peptide related to cholecystokinin (Boel and colleagues, PNAS 1983). The N-terminal extension of G34 — the region encompassing this [1-8] fragment — was subsequently exploited to develop N-terminus-directed antisera capable of distinguishing G34 from G17 in antral tissue and plasma by radioimmunoassay, enabling more precise studies of gastrin secretion and metabolism.
What it does
Gastrin-34 [1-8] lacks the C-terminal receptor-activating pharmacophore present in all biologically active gastrin and CCK peptides. That pharmacophore — the amidated C-terminal pentapeptide (Gly-Trp-Met-Asp-Phe-NH₂) shared by every active gastrin and CCK form — is the minimal sequence required to activate cholecystokinin receptors; it is not present in this fragment (Zeng and colleagues, Frontiers in Endocrinology 2020; Miller and colleagues, Pharmacology & Therapeutics 2008). Studies of the closely related N-terminal 1–17 tryptic fragment of big gastrin, which includes the [1-8] region, confirmed that it has no effect on basal gastric acid output or gastrin-17-evoked acid secretion when infused in human volunteers at a range of doses (Gastroenterology 1984). The primary use of the [1-8] fragment is therefore as a biochemical and immunological reference peptide: its sequence is selectively recognized by N-terminus-directed antibodies that discriminate G34 from G17, and the N-terminal region of G34 is where trypsin-like proteases cleave during post-translational processing and metabolic turnover.
Evidence
- Human: No direct human pharmacology data exist for the isolated [1-8] fragment. The N-terminal 1–17 tryptic fragment of big gastrin (which includes this sequence) was infused in human volunteers and showed rapid plasma clearance and no measurable effect on gastric acid secretion (Gastroenterology 1984).
- In vitro: N-terminal G34-specific antisera with antigenic determinants within the 1–6 and 1–12 regions have been characterized and used to quantify G34-derived peptides in antral tissue extracts and plasma by radioimmunoassay. Concentrations of the N-terminal tryptic fragment in human antral mucosa were found to be broadly similar to those of gastrin-17 in the same extracts. No receptor-binding or cell-signaling data have been reported for the isolated [1-8] peptide.
Mechanism
Full-length gastrin-34 activates the cholecystokinin-2 receptor (CCK2R, also called the gastrin receptor or CCK-B receptor), a class A G-protein-coupled receptor expressed on gastric parietal cells and enterochromaffin-like cells that drives acid secretion and histamine release. The essential binding pharmacophore involves the C-terminal tetrapeptide amide shared by all active gastrins; the N-terminal arm of G34 — which includes the [1-8] segment — contributes to circulating half-life and metabolic processing but is not part of the receptor-binding interface (Miller and colleagues, Pharmacology & Therapeutics 2008; Zeng and colleagues, Frontiers in Endocrinology 2020). The card's CCK1R (CCKA) target reflects the broader gastrin–CCK receptor family context. In intact gastrin physiology, CCK1R (expressed on gallbladder smooth muscle and vagal afferents) is the primary receptor for sulfated CCK peptides, mediating gallbladder contraction and satiety signalling, while gastrin's own dominant receptor is CCK2R; gastrin peptides bind CCK1R with roughly 500–10,000-fold lower affinity than sulfated CCK (Miller and colleagues, Pharmacology & Therapeutics 2008). The [1-8] fragment, lacking the C-terminal pharmacophore entirely, has no agonist activity at either receptor subtype. Its generation in vivo results from trypsin-like protease cleavage at the Lys-Lys dibasic motif in the G34 precursor, a processing step delineated by the molecular cloning of preprogastrin (Boel and colleagues, PNAS 1983).
Open questions
- No specific binding partner or receptor has been identified for N-terminal gastrin processing fragments including this peptide.
- Whether the G34-specific N-terminal region plays any structural role in precursor folding or secretory granule packaging has not been investigated.
- The functional significance of gastrin-34 N-terminal immunoreactivity detected in brain tissue by N-terminus-specific antibodies remains unexplained.
Related peptides
- [Gastrin-34 [1-9] peptide](/card/pep-10614) — the one-residue C-terminal extension of this fragment, covering the same unique G34 N-terminal arm.
- Gastrin-34 peptide — the full 34-residue form, which includes this fragment at its N-terminus and carries the complete C-terminal pharmacophore.
- Minigastrin I — a C-terminal fragment of gastrin-17 that retains the full receptor-binding pharmacophore; studied as a scaffold for CCK2R-targeted radiotracers.
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.
Was the CCKAR receptor target actually tested for this short fragment, or just assumed based on the larger molecule it comes from?
If the annotation is unverified, researchers using this fragment to study CCK receptors could be drawing conclusions from a tool that has no real receptor activity, potentially explaining inconsistent results across labs working on gastrin biology.
Is this 7-residue fragment more resistant to being broken down by gut enzymes than the 8- and 9-residue versions, despite being shorter?
If the shortest fragment is the most stable, it is likely the one that actually accumulates in the stomach and intestine during normal physiology, meaning it is the most relevant target for understanding the biological roles of gastrin-34 processing fragments.
Is this 7-residue fragment the minimum length needed to display the special shape that makes big gastrin immunologically unique?
Knowing the minimum structural unit for big gastrin recognition could lead to smaller, cheaper, and more specific diagnostic reagents for distinguishing gastrin forms in patient blood, improving accuracy of tests for stomach acid disorders.
Could this fragment slow down a gut enzyme that normally breaks down other signaling molecules in the intestine?
If this fragment inhibits the gut enzyme PEP, it could affect how the intestine processes inflammation signals and food-derived proteins, which is relevant to conditions like celiac disease and inflammatory bowel disease.
▸full evidence table2 metrics
| metric | value | tool |
|---|---|---|
| ipTM | 0.9516605734825134 | boltz-2 |
| ranking score | 0.7952330112457275 | boltz-2 |
▸structural qualityopenfold3
| metric | value | note |
|---|---|---|
| gpde | 0.717 | 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{pep10613,
sequence = {LGPQGPP},
target = {cckar},
author = {peptidemodel},
year = {2026},
status = {synthesized}
}