Yamile Gonzlez, Tirso Pons, Jeovanis Gil, Vladimir Besada, Maday Alonso-del-Rivero, Aparecida S. Tanaka, Mariana S. Araujo, Mara A. Chvez
Characterization and comparative 3D modelling of CmPI-II, a novel 'nonclassical' Kazal-type inhibitor from the marine snail Cenchritis muricatus (Mollusca)
The complete amino acid sequence -obtained by ESI-MS/MS- of the proteinase inhibitor CmPI-II isolated from Cenchritis muricatus is described. CmPI-II is a 5480 Da protein with three disulfide bridges, which inhibits human neutrophil elastase (HNE) (Ki 2.6±0.2 nM), trypsin (Ki 1.1±0.9 nM), and other serine proteinases such as subtilisin A (Ki 30.8±1.2 nM) and pancreatic elastase (Ki 145.0±4.4 nM); chymotrypsin, pancreatic and plasma kallikreins, thrombin and papain are not inhibited. CmPI-II shares homology to the Kazal-type domain and may define a new group for the 'nonclassical' Kazal inhibitors, according to its CysICysV disulfide bridge position. The 3D-model of CmPI-II exhibits similar secondary structure characteristics to the Kazal type inhibitors and concurs with circular dichroism experiments. The 3D-model of CmPI-II/HNE complex provided a structural framework for the interpretation of its experimentally determined Ki value. The model showed both similar and different contacts at the primary binding sites in comparison with the structure of turkey ovomucoid third domain (OMTKY3)/HNE, used as template. Additional contacts calculated at the protease-inhibitor interface could also contribute to the association energy of the complex. This inhibitor represents an exception in terms of specificity, due to its ability to inhibit strongly elastases and trypsin.
Biological Chemistry, Walter de Gruyter
Print ISSN: 1431-6730
Volume: 2007
Pages: -
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