Insulin Like Growth Factor Binding Protein, Acid Labile Subunit (IGFALS)

Until birth, binary IGFBP/IGF complexes of 50 kD predominate in serum, with IGFBP2 being the most frequently occurring IGFBP moiety. In juvenile and adult mammals, however, 80% to 85% of serum IGFs are found in a ternary complex of 150 kD composed of 1 molecule each of IGF, IGFBP3, and a protein that is found only in serum, the acid-labile subunit (ALS). ALS migrates at an apparent molecular mass of 84-86 kD. ALS cDNAs predict signal peptide and mature protein of 23 and 580 amino acids in the rat, and 27 and 578 amino acids in humans. ALS retains the IGFBP3/IGF complexes in the vascular compartment and extends the half life of IGFs in the circulation. Synthesis of ALS occurs mainly in liver after birth and is stimulated by growth hormone