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Three-dimensional structure of an unusual Kunitz (STI) type trypsin inhibitor from Copaifera langsdorffii
Sandra Krauchenco1, Ronaldo A P Nagem, José A da Silva
1Grupo de Cristalografia, Department of Physics and Informatics, Institute of Physics (IFSC), University of Sao Paulo, Avenue Trabalhador Saocarlense, 400, CEP 13560-970, Sao Carlos, SP, Brazil.
Abstract:
The crystallographic structure of a novel trypsin inhibitor (CTI) from Copaifera langsdorffii is reported. The structure was solved by MIRAS procedure and refined to a crystallographic residual of 17.3% (R(free) = 20.3%) at 1.8 A resolution. Two isomorphous derivatives were obtained by quick cryo-soaking approach. CTI is the first structure of a member of Kunitz (STI) family formed by two noncovalently bound polypeptide chains and only one disulfide bridge. A standard Kunitz-type inhibitor has a single polypeptide chain and two disulfide bridges. Structural features granting CTI high inhibitory activity are discussed.
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