K4 Elite
K4 Elite
A synthetic 83-amino-acid analog of insulin-like growth factor 1, engineered with an N-terminal extension and an Arg substitution at position 3 to reduce binding to IGF binding proteins and extend its circulating half-life in research models.
IGF-1 LR3 is a laboratory-modified analog of native insulin-like growth factor 1 (IGF-1). It differs from the endogenous hormone by the addition of a 13-amino-acid extension peptide at the N-terminus and the replacement of the glutamic acid at position 3 with an arginine residue. These modifications were introduced by researchers to markedly reduce the analog's affinity for insulin-like growth factor binding proteins (IGFBPs).
Because native IGF-1 in circulation is largely bound to IGFBPs, its free (bioavailable) fraction is tightly regulated. The reduced IGFBP binding of the LR3 variant has been used in cell-culture and animal studies to produce a longer functional presence relative to unmodified IGF-1, making it a common reagent in growth-factor signaling research.
The compound is studied strictly as a research chemical for in vitro and preclinical investigation of the IGF-1 signaling axis.
Native IGF-1 and its analogs act principally through the IGF-1 receptor (IGF-1R), a receptor tyrosine kinase. Ligand binding triggers autophosphorylation and activation of downstream cascades including the PI3K/Akt and Ras/MAPK pathways, which in experimental systems are associated with cellular proliferation, differentiation, and survival signaling.
The distinguishing feature of the LR3 analog is its diminished binding to IGFBPs. In reference studies, this altered binding profile increases the proportion of the analog available to interact with IGF-1R in cell culture, which is the basis for its use as a persistent IGF-1R agonist in laboratory models.
These summaries describe published laboratory and preclinical studies for informational purposes only and are not instructions for use.
In biotechnology process research, Long-R3-IGF-1 has been evaluated as a component of serum-free and animal-component-free cell-culture media; published bioprocess literature reports it as a mitogenic supplement supporting mammalian cell growth in bioreactor systems (Morris & Schmid, 2000, describing LongR3IGF-I as a culture supplement).
Foundational characterization work by Francis and colleagues described the reduced IGFBP affinity and enhanced in vitro potency of N-terminally extended and position-3-substituted IGF-1 analogs relative to native IGF-1, establishing the molecular rationale for the LR3 modification.
Combinations examined in the research literature. Descriptive only — not a recommendation to combine compounds.
References are being compiled for this entry.