title: Characterization and comparative 3D modeling of CmPI-II, a novel 'non-classical' Kazal-type inhibitor from the marine snail Cenchritis muricatus (Mollusca).
abstract: The complete amino acid sequence obtained by electrospray ionization tandem mass spectrometry of the proteinase inhibitor CmPI-II isolated from Cenchritis muricatus is described. CmPI-II is a 5480-Da protein with three disulfide bridges that inhibits human neutrophil elastase (HNE) (K(i) 2.6+/-0.2 nM), trypsin (K(i) 1.1+/-0.9 nM), and other serine proteinases such as subtilisin A (K(i) 30.8+/-1.2 nM) and pancreatic elastase (K(i) 145.0+/-4.4 nM); chymotrypsin, pancreatic and plasma kallikreins, thrombin and papain are not inhibited. CmPI-II shares homology with the Kazal-type domain and may define a new group of 'non-classical' Kazal inhibitors according to its Cys(I)-Cys(V) disulfide bridge position. The 3D model of CmPI-II exhibits similar secondary structure characteristics to Kazal-type inhibitors and concurs with circular dichroism experiments. A 3D model of the CmPI-II/HNE complex provides a structural framework for the interpretation of its experimentally determined K(i) value. The model shows 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 owing to its ability to strongly inhibit elastases and trypsin.
authors.affiliation: Centro de Estudio de Proteínas (CEP), Facultad de Biología, Universidad de La Habana, Calle 25 No 455, Vedado, Habana, Cuba. yamile@fbio.uh.cu
authors.forename: Yamile
authors.initials: Y
authors.lastname: González
authors.forename: Tirso
authors.initials: T
authors.lastname: Pons
authors.forename: Jeovanis
authors.initials: J
authors.lastname: Gil
authors.forename: Vladimir
authors.initials: V
authors.lastname: Besada
authors.forename: Maday
authors.initials: M
authors.lastname: Alonso-del-Rivero
authors.forename: Aparecida S
authors.initials: AS
authors.lastname: Tanaka
authors.forename: Mariana S
authors.initials: MS
authors.lastname: Araujo
authors.forename: María A
authors.initials: MA
authors.lastname: Chávez
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002942:Circular Dichroism; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D019272:Leukocyte Elastase / Q000037:antagonists & inhibitors; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid; D012908:Snails; D021241:Spectrometry, Mass, Electrospray Ionization; D013056:Spectrophotometry, Ultraviolet; D053719:Tandem Mass Spectrometry; D014359:Trypsin Inhibitor, Kazal Pancreatic / Q000737:chemistry* / Q000302:isolation & purification / Q000494:pharmacology
chemical_list: D014359:Trypsin Inhibitor, Kazal Pancreatic; D019272:Leukocyte Elastase