Human alpha₂-Macroglobulin Antibody

Human alpha₂-macroglobulin (h alpha2M) is a serum glycoprotein that has sequence similarity to other members of the alpha2M family including complement components C3, C4 and C5 (1). alpha2M is synthesized as a polypeptide of 1474 amino acids with a signal peptide (23 residues) (2). The mature protein is a tetramer (720 kDa) of 4 identical subunits (180 kDa), which form two disulfide bond-linked dimers. As a general and irreversible protease inhibitor implicated in many processes, alpha2M is able to inhibit all four classes of proteases by a unique trapping mechanism. The bait region of h alpha2M (residues 690‑728) contains specific cleavage sites for different proteases. The cleavage of the bait region by a protease induces a conformation change in alpha2M, which then traps and forms a covalent bond with the protease. The trapped protease remains active against small peptide substrates but loses its ability to interact with large protein substrates or inhibitors.