1BIK

X-RAY STRUCTURE OF BIKUNIN FROM THE HUMAN INTER-ALPHA-INHIBITOR COMPLEX

Summary for 1BIK

• Entry DOI: 10.2210/pdb1bik/pdb
• Descriptor: BIKUNIN, 2-acetamido-2-deoxy-beta-D-glucopyranose, SULFATE ION, ... (4 entities in total)
• Functional Keywords: glycoprotein, bikunin, trypstatin, urinary trypsin inhibitor, uronic-acid-rich protein, serine protease inhibitor (kunitz type), glycosylated protein
• Biological source: Homo sapiens (human)
• Cellular location: Secreted: P02760
• Total number of polymer chains: 1
• Total formula weight: 16400.34

Authors

Xu, Y.,Carr, P.D.,Guss, J.M.,Ollis, D.L. (deposition date: 1997-11-26, release date: 1999-03-16, Last modification date: 2024-11-20)

Primary citation

Xu, Y.,Carr, P.D.,Guss, J.M.,Ollis, D.L.
The crystal structure of bikunin from the inter-alpha-inhibitor complex: a serine protease inhibitor with two Kunitz domains.
J.Mol.Biol., 276:955-966, 1998

PubMed Abstract: Bikunin is a serine protease inhibitor found in the blood serum and urine of humans and other animals. Its sequence shows internal repetition, suggesting that it contains two domains that resemble bovine pancreatic trypsin inhibitor (BPTI). A fragment of bikunin has been crystallised, its structure solved and subsequently refined against 2.5 A data. The two BPTI-like domains pack closely together and are related by an approximate 60 degrees rotation combined with a translation. These domains are very similar to each other and other proteins with this fold. The largest variations occur in the loops responsible for protease recognition. The loops of the first domain are unobstructed by the remaining protein. However, the loops of the second domain are close to the first domain and it is possible that protease binding may be affected or, in some cases, abolished by the presence of the first domain. Thus, cleavage of the two domains could alter the substrate specificity of domain II. Bikunin has a hydrophobic patch close to the N terminus of domain I, which is the most likely site for cell-surface receptor binding. In addition, there is a basic patch at one end of domain II that may be responsible for the inhibition of calcium oxalate crystallization in urine.

PubMed: 9566199
DOI: 10.1006/jmbi.1997.1582

Experimental method

X-RAY DIFFRACTION (2.5 Å)