The precursor is proteolytically processed into separatelyfunctioning proteins.
3-hydroxykynurenine, an oxidized tryptophan metabolite thatis common in biological fluids, reacts with Cys-53, Lys-111,Lys-137, and Lys-149 to form heterogeneous polycyclic chromophoresincluding hydroxanthommatin. The reaction by alpha-1-microglobulinis autocatalytic; the human protein forms chromophore even whenexpressed in insect and bacterial cells. The chromophore can reactwith accessible cysteines forming non-reducible thioethercross-links with other molecules of alpha-1-microglobulin or withother proteins such as Ig alpha-1 chain C region 'Cys-352'.
Heavy chains are interlinked with bikunin via a chondroitin4-sulfate bridge to the their C-terminal aspartate (By similarity).
N- and O-glycosylated. N-glycan heterogeneity at Asn-115:Hex5HexNAc4 (major), Hex6HexNAc5 (minor) and dHex1Hex6HexNAc5(minor). N-glycan at Asn-250: Hex5HexNAc4. O-linkage of theglycosaminoglycan, chondroitin sulfate, at Ser-215 allowscross-linking between the three polypeptide chains.