Mechano growth factor is the twenty-four residue C-terminal extension of the IGF-1Ec splice variant, studied on its own as a synthetic peptide. It arises when mechanical loading or damage in skeletal muscle shifts IGF-1 splicing toward the Ec exon, and the E domain is then liberated from the mature IGF-1 chain by proteolysis. The pegylated form, PEG-MGF, carries a polyethylene glycol chain added to extend a serum half-life measured in minutes.
Key facts
| Type | C-terminal E domain peptide of the IGF-1Ec splice variant |
| Amino acid count | 24 |
| Sequence | Tyr-Gln-Pro-Pro-Ser-Thr-Asn-Lys-Asn-Thr-Lys-Ser-Gln-Arg-Arg-Lys-Gly-Ser-Thr-Phe-Glu-Glu-Arg-Lys |
| Calculated average mass | 2868 g/mol for the free peptide |
| Pegylated form | PEG-MGF, typically a 5 kDa methoxy-PEG chain, giving roughly 8 kDa total |
| Parent transcript | IGF1 transcript with exon 5 retained, known as IGF-1Ec in humans |
| Net charge | Strongly basic, with six arginine and lysine residues in the central region |
| Synonyms | MGF, IGF-1Ec E domain peptide, IGF-1 Ec, mechano growth factor |
Structure and chemistry
The IGF1 gene produces several transcripts that share the mature IGF-1 coding region and differ in the E domain encoded downstream. In humans the variant that retains exon 5 is called IGF-1Ec, and the peptide studied as mechano growth factor is the final twenty-four residues of that E domain. The sequence is unusually basic for its length, with a run of arginine and lysine residues in the middle that dominates its chromatographic and binding behaviour.
Two properties follow from that composition. The peptide binds heparin and other polyanions strongly, which is exploited in purification and is also why it adheres to glassware and to negatively charged plastics from dilute solution. It is also cleared rapidly, with reported serum half-lives of a few minutes, because a short basic peptide with no structured fold is a straightforward substrate for circulating peptidases and for renal filtration.
PEG-MGF addresses the second property. A methoxy-polyethylene glycol chain, most often 5 kDa, is coupled to the N-terminal amine or to a lysine side chain, taking the conjugate to roughly 8 kDa and shielding the peptide backbone from proteases. Pegylation chemistry is not site-uniform unless a specific handle is engineered, so preparations are mixtures of positional isomers and analytical characterisation reports a distribution and not a single species. Certificates for pegylated material should state the PEG mass and the coupling chemistry, since neither can be read from a purity figure.
Mechanism of action
The E domain peptide does not bind the type 1 IGF receptor. Receptor contact in IGF-1 is made by the B and A domains of the mature chain, all of which are absent here, and MGF produces no IGF-1 receptor autophosphorylation in cells that respond strongly to intact IGF-1. That separation is the reason the peptide is studied on its own: it isolates whatever the E domain contributes from the well characterised receptor arm.
Reported activity in myoblast culture centres on satellite cell behaviour. The peptide has been described as increasing myoblast proliferation while delaying differentiation, a combination opposite to the pro-differentiation effect of mature IGF-1, and as raising markers of satellite cell activation after mechanical or chemical injury. Proposed mediators include a distinct cell surface binding site and nucleolar localisation of the basic sequence, neither of which has been resolved to a defined receptor. Independent replication has been uneven, and the compound is used in cell work partly to test that literature.
Research applications
- Myoblast proliferation assays measuring bromodeoxyuridine incorporation or nuclear count in C2C12 and primary satellite cell culture.
- Differentiation time courses tracking myogenin and myosin heavy chain to test the reported delay in fusion.
- IGF-1 receptor selectivity screens confirming absence of receptor autophosphorylation and AKT activation.
- Serum stability comparison of the free peptide against pegylated conjugate by LC-MS over minutes to hours.
- Heparin and polyanion binding characterisation, including recovery losses from dilute solution onto labware.
- Characterisation of pegylation positional isomers by ion exchange chromatography and peptide mapping.
Compounds studied around growth factor signalling sit in NuVion’s Growth Hormones category.
Handling in the laboratory
Both forms are supplied lyophilised and reconstituted with bacteriostatic water added slowly down the wall of the vial, then swirled without shaking. The reconstitution calculator converts vial content and diluent volume into a stock concentration. Highly basic peptides adsorb to untreated glass and to some plastics, so working dilutions are prepared in low-binding tubes and, where the assay permits, in buffer containing a carrier protein.
The free peptide is the less stable of the two in any solution containing serum or tissue lysate, and stock intended for repeat use is aliquoted at first reconstitution and not returned to the freezer. Pegylated material tolerates handling better but is heterogeneous, so aliquots are drawn from a thoroughly mixed stock; PEG conjugates can stratify in a partially thawed vial and give inconsistent concentrations between draws from the same tube.
Testing and supply from NuVion
NuVion supplies a tested range across the growth hormone axis and its downstream mediators, including IGF-1 LR3, HGH, CJC-1295 No DAC and Ipamorelin. That range is manufactured at a GMP-audited facility and independently tested by Janoshik Analytical, with purity determined by RP-HPLC and identity confirmed by mass spectrometry, and the certificates are published in the Certificate of Analysis library. MGF and PEG-MGF are not part of the current catalogue and this page is a reference profile.
Related compounds
The mature chain that the E domain is spliced onto is covered in IGF-1 LR3, the analogue with an extended N-terminus and reduced binding protein affinity. Upstream, HGH drives hepatic IGF-1 transcription, and CJC-1295, sermorelin and ipamorelin act on its release. For muscle and connective tissue repair endpoints, see TB-500 and BPC-157.
Frequently asked questions
What is the difference between MGF and PEG-MGF?
The peptide sequence is identical. PEG-MGF carries a polyethylene glycol chain, usually 5 kDa, coupled to an amine on the peptide. The conjugate resists peptidases and is filtered by the kidney more slowly, so it persists in serum for hours where the free peptide persists for minutes. Receptor-level behaviour is unchanged; what changes is exposure time in any system containing proteases.
Is MGF the same as IGF-1?
No. IGF-1 is the 70 residue mature protein that binds and activates the type 1 IGF receptor. MGF is the 24 residue E domain extension from one splice variant of the same gene, studied after separation from the mature chain. It carries none of the receptor binding surface and does not activate the IGF-1 receptor.
Why does MGF adsorb to labware?
Six of its twenty-four residues are arginine or lysine, giving a strongly basic peptide with no folded structure to bury that charge. It binds negatively charged surfaces, including untreated glass and some plastics, and at low concentration a measurable fraction of a dilute solution can be lost to the tube wall. Low-binding consumables and a carrier protein in the buffer address it.
Is MGF listed in the Australian Register of Therapeutic Goods?
No. Neither MGF nor PEG-MGF is included in the Australian Register of Therapeutic Goods, and neither has been assessed by the Therapeutic Goods Administration for quality, safety or efficacy. Material of this class is supplied in Australia as a laboratory chemical for in vitro research.
Research use only. The compound described on this page is discussed as a laboratory chemical used in in vitro research. It is not included in the Australian Register of Therapeutic Goods and has not been assessed by the Therapeutic Goods Administration for quality, safety or efficacy. It is not for human or veterinary use, and nothing on this page is a representation about therapeutic use.
