|Detection of Human Bikunin by Western Blot. Western blot shows human urine. PVDF membrane was probed with 0.5 µg/mL of Sheep Anti-Human Bikunin Antigen Affinity-purified Polyclonal Antibody (Catalog # AF7744) followed by HRP-conjugated Anti-Sheep IgG Secondary Antibody (Catalog # HAF016). A specific band was detected for Bikunin at approximately 35-45 kDa (as indicated). This experiment was conducted under reducing conditions and using Immunoblot Buffer Group 1.|
Bikunin (also known as I alpha I light chain, EDC1, HI30 and Trypstatin) is a secreted, 35-45 kDa proteoglycan member of the kunin family of serine protease inhibitors. It is expressed by hepatocytes, amniotic epithelium and mesothelial cells. Bikunin possesses both sulfated and nonsulfated GAG sequences. The nonsulfated sequences are known to form ester linkages with two 80 kDa "heavy" chains in the hepatocyte Golgi, forming 180-200 kDa I alpha I. This molecule participates in the formation of hyaluronan-containing ECM. In addition, one of the H chains of I alpha I can be displaced by TSG6, creating an antiplasmin complex. Human bikunin is generated through cleavage of a precursor molecule termed AMBP. This AMBP should not be confused with AMBP-1, a 120-140 kDa adrenomedullin-binding protein that is also known as Complement Factor H. The AMBP precursor contains a 19 aa signal sequence, an N-terminal 183 aa A1M protein (aa 20-203), and the C-terminal serine protease inhibitor bikunin (aa 206-352). Bikunin possesses one GAG attachment site at Ser215, two Kunitz inhibitor domains (aa 231-281 and 287-337) and one utilized N-linked glycosylation site at Asn250. Although cleavage of AMBP in the Golgi may result in release of free bikunin, the 60-65 kDa AMBP precursor can also be released intact. Over aa 206-352, human bikunin shares 77% aa sequence identity with mouse bikunin.