1bik
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(New page: 200px<br /> <applet load="1bik" size="450" color="white" frame="true" align="right" spinBox="true" caption="1bik, resolution 2.5Å" /> '''X-RAY STRUCTURE OF B...)
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Revision as of 14:03, 12 November 2007
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X-RAY STRUCTURE OF BIKUNIN FROM THE HUMAN INTER-ALPHA-INHIBITOR COMPLEX
Overview
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.
About this Structure
1BIK is a Single protein structure of sequence from Homo sapiens with NAG and SO4 as ligands. Full crystallographic information is available from OCA.
Reference
The crystal structure of bikunin from the inter-alpha-inhibitor complex: a serine protease inhibitor with two Kunitz domains., Xu Y, Carr PD, Guss JM, Ollis DL, J Mol Biol. 1998 Mar 13;276(5):955-66. PMID:9566199
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