IGF-1 LR3 (Long Arg3 IGF-1) is an 83-amino acid synthetic analog of human Insulin-like Growth Factor-1, modified through two structural changes: a glutamate-to-arginine substitution at position 3 (Arg³) and a 13-amino acid N-terminal extension peptide. Native IGF-1 is a 70-amino acid single-chain polypeptide structurally related to insulin that mediates many of the growth-promoting effects of growth hormone through endocrine, paracrine, and autocrine signaling. The modifications in IGF-1 LR3 specifically target the IGF binding protein (IGFBP) interaction domain — by disrupting IGFBP binding, the analog achieves dramatically increased bioavailability compared to native IGF-1 in biological research systems.
In circulation and tissue compartments, native IGF-1 is almost entirely bound to a family of six IGF binding proteins (IGFBP-1 through IGFBP-6), which regulate its bioavailability, tissue distribution, and receptor access. IGFBP-3, the most abundant carrier, sequesters >95% of circulating IGF-1 in a ternary complex with the acid-labile subunit (ALS). The Arg³ substitution and N-terminal extension in IGF-1 LR3 reduce IGFBP binding affinity by over 100-fold, resulting in a predominantly free (unbound) peptide that can freely interact with the IGF-1 receptor. This translates to approximately 2-3 times greater potency in cell proliferation assays and makes IGF-1 LR3 the preferred form for cell culture applications where IGFBP levels can unpredictably sequester native IGF-1.
IGF-1 LR3 retains full agonist activity at the IGF-1 receptor (IGF1R), a receptor tyrosine kinase that activates two major downstream signaling cascades: the PI3K/Akt/mTOR pathway (cell survival, protein synthesis, glucose uptake) and the Ras/MAPK/ERK pathway (cell proliferation, differentiation). Research applications include cell culture supplementation (serum-free and serum-reduced media), myogenesis and muscle cell differentiation studies, cancer biology (IGF1R-dependent proliferation), stem cell research, and metabolic signaling.
Supplied as a lyophilized powder with ≥99% purity. Store at -20°C. For cell biology and growth factor research only.
