IGF-1 LR3

Molecular structure

IGF-1 LR3 is a modified form of insulin-like growth factor 1. Native IGF-1 contains 70 residues, whereas LR3 includes a 13-residue amino-terminal extension and a substitution of arginine for glutamic acid at position 3.

The molecule retains the characteristic structural organization of the insulin/IGF protein family. Three intramolecular disulfide bonds contribute to the folded structure.

Disulfide bonds form through oxidation of cysteine side chains and can stabilize a protein's conformation. Incorrect disulfide pairing can produce molecules with the expected amino-acid composition but an altered three-dimensional structure.

Physicochemical properties

The molecule's behavior depends on its folded state, disulfide-bond connectivity, pH, and solvent environment. Its larger size and structured fold distinguish it from short linear peptides.

The amino-terminal extension and residue substitution can alter interactions with binding proteins and receptors. These effects should be established experimentally rather than inferred from sequence length alone.

Biochemical mechanisms

IGF-1 receptor binding can activate receptor tyrosine kinase signaling. Receptor autophosphorylation can initiate downstream signaling involving PI3K-AKT and RAS-MAPK.

The exact binding properties of IGF-1 LR3 depend on the integrity of its folded structure and the experimental system used to measure receptor interactions.

Scientific evidence

Its relationship to IGF-1 and its defining sequence modifications are established. Correct folding and disulfide connectivity are important additional identity criteria.