Crystal structures of a plant trypsin inhibitor from Enterolobium contortisiliquum (EcTI) and of its complex with bovine trypsin

A serine protease inhibitor from Enterolobium contortisiliquum (EcTI) belongs to the Kunitz family of plant inhibitors, common in plant seeds. It was shown that EcTI inhibits the invasion of gastric cancer cells through alterations in integrin-dependent cell signaling pathway. We determined high-res...

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Bibliographic Details
Published in:PloS one 2013-04, Vol.8 (4), p.e62252-e62252
Main Authors: Zhou, Dongwen, Lobo, Yara A, Batista, Isabel F C, Marques-Porto, Rafael, Gustchina, Alla, Oliva, Maria L V, Wlodawer, Alexander
Format: Article
Language:English
Subjects:
Amino Acid Sequence
Amino acids
Analysis
Animals
Biology
Catalytic Domain
Cattle
Cellular signal transduction
Conformation
Crystal structure
Crystallization
Crystallography
Crystallography, X-Ray
Electron density
Enterolobium contortisiliquum
Enzymes
Evaluation
Fabaceae - chemistry
Fibroblasts
Gastric cancer
Inhibitors
Integrins
Kinases
Laboratories
Materials Science
Medical research
Models, Molecular
Molecular Conformation
Molecular Sequence Data
Polypeptides
Protease inhibitors
Proteases
Protein Binding
Protein Conformation
Proteins
Redundancy
Rigid-body dynamics
Rotating bodies
Seeds
Sequence Alignment
Serine
Serine Proteases - chemistry
Serine Proteases - metabolism
Serine proteinase
Signal transduction
Signaling
Stomach cancer
Trypsin
Trypsin - chemistry
Trypsin - metabolism
Trypsin inhibitors
Trypsin Inhibitors - chemistry
Trypsin Inhibitors - metabolism
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Summary:A serine protease inhibitor from Enterolobium contortisiliquum (EcTI) belongs to the Kunitz family of plant inhibitors, common in plant seeds. It was shown that EcTI inhibits the invasion of gastric cancer cells through alterations in integrin-dependent cell signaling pathway. We determined high-resolution crystal structures of free EcTI (at 1.75 Å) and complexed with bovine trypsin (at 2 Å). High quality of the resulting electron density maps and the redundancy of structural information indicated that the sequence of the crystallized isoform contained 176 residues and differed from the one published previously. The structure of the complex confirmed the standard inhibitory mechanism in which the reactive loop of the inhibitor is docked into trypsin active site with the side chains of Arg64 and Ile65 occupying the S1 and S1' pockets, respectively. The overall conformation of the reactive loop undergoes only minor adjustments upon binding to trypsin. Larger deviations are seen in the vicinity of Arg64, driven by the needs to satisfy specificity requirements. A comparison of the EcTI-trypsin complex with the complexes of related Kunitz inhibitors has shown that rigid body rotation of the inhibitors by as much as 15° is required for accurate juxtaposition of the reactive loop with the active site while preserving its conformation. Modeling of the putative complexes of EcTI with several serine proteases and a comparison with equivalent models for other Kunitz inhibitors elucidated the structural basis for the fine differences in their specificity, providing tools that might allow modification of their potency towards the individual enzymes.
ISSN:1932-6203
1932-6203
DOI:10.1371/journal.pone.0062252