THREE-DIMENSIONAL STRUCTURE OF THE COMPLEXES BETWEEN BOVINE CHYMOTRYPSINOGEN*A AND TWO RECOMBINANT VARIANTS OF HUMAN PANCREATIC SECRETORY TRYPSIN INHIBITOR (KAZAL-TYPE)
[ISK1_HUMAN] Defects in SPINK1 are a cause of pancreatitis (PCTT) [MIM:167800]. A disease characterized by the presence of calculi in pancreatic ducts. It causes severe abdominal pain attacks.   Defects in SPINK1 are the cause of susceptibility to tropical calcific pancreatitis (TCP) [MIM:608189]. TCP is an idiopathic, juvenile, nonalcoholic form of chronic pancreatitis widely prevalent in several tropical countries. It can be associated with fibrocalculous pancreatic diabetes (FCPD) depending on both environmental and genetic factors. TCP differs from alcoholic pancreatitis by a much younger age of onset, pancreatic calcification, a high incidence of insulin dependent but ketosis resistant diabetes mellitus, and an exceptionally high incidence of pancreatic cancer. 
[ISK1_HUMAN] This is a trypsin inhibitor, its physiological function is to prevent the trypsin-catalyzed premature activation of zymogens within the pancreas.
Publication Abstract from PubMed
Variants of the human pancreatic secretory trypsin inhibitor (PSTI) have been created during a protein design project to generate a high-affinity inhibitor with respect to some serine proteases other than trypsin. Two modified versions of human PSTI with high affinity for chymotrypsin were crystallized as a complex with chymotrypsinogen. Both crystallize isomorphously in space group P4(1)2(1)2 with lattice constants a = 84.4 A, c = 86.7 A and diffract to 2.3 A resolution. The structure was solved by molecular replacement. The final R-value after refinement with 8.0 to 2.3 A resolution data was 19.5% for both complexes after inclusion of about 50 bound water molecules. The overall three-dimensional structure of PSTI is similar to the structure of porcine PSTI in the trypsinogen complex (1TGS). Small differences in the relative orientation of the binding loop and the core of the inhibitors indicate flexible adaptation to the proteases. The chymotrypsinogen part of the complex is similar to chymotrypsin. After refolding induced by binding of the inhibitor the root-mean-square difference of the active site residues A186 to A195 and A217 to A222 compared to chymotrypsin was 0.26 A.
Three-dimensional structure of the complexes between bovine chymotrypsinogen A and two recombinant variants of human pancreatic secretory trypsin inhibitor (Kazal-type).,Hecht HJ, Szardenings M, Collins J, Schomburg D J Mol Biol. 1991 Aug 5;220(3):711-22. PMID:1870127
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.