Document Detail

Solution structure of a Kunitz-type chymotrypsin inhibitor isolated from the elapid snake Bungarus fasciatus.
MedLine Citation:
PMID:  11562364     Owner:  NLM     Status:  MEDLINE    
Bungarus fasciatus fraction IX (BF9), a chymotrypsin inhibitor, consists of 65 amino acid residues with three disulfide bridges. It was isolated from the snake venom of B. fasciatus by ion-exchange chromatography and belongs to the bovine pancreatic trypsin inhibitor (BPTI)-like superfamily. It showed a dissociation constant of 5.8 x 10(-8) m with alpha-chymotrypsin as measured by a BIAcore binding assay system. The isothermal titration calorimetry revealed a 1:1 binding stoichiometry between this inhibitor and chymotrypsin and apparently no binding with trypsin. We further used CD and NMR to determine the solution structure of this venom-derived chymotrypsin inhibitor. The three-dimensional NMR solution structures of BF9 were determined on the basis of 582 restraints by simulated annealing and energy minimization calculations. The final set of 10 NMR structures was well defined, with average root mean square deviations of 0.47 A for the backbone atoms in the secondary structure regions and 0.86 A for residues The side chains of Phe(23), Tyr(24), Tyr(25), Phe(35), and Phe(47) exhibited many long-range nuclear Overhauser effects and were the principal components of the hydrophobic core in BF9. To gain insight into the structure-function relationships among proteins in the BPTI-like superfamily, we compared the three-dimensional structure of BF9 with three BPTI-like proteins that possess distinct biological functions. These proteins possessed similar secondary structure elements, but the loop regions and beta-turn were different from one another. Based on residues at the functional site of each protein, we suggest that the flexibility, rigidity, and variations of the amino acid residues in both the loop and beta-turn regions are related to their biological functions.
C Chen; C H Hsu; N Y Su; Y C Lin; S H Chiou; S H Wu
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2001-09-18
Journal Detail:
Title:  The Journal of biological chemistry     Volume:  276     ISSN:  0021-9258     ISO Abbreviation:  J. Biol. Chem.     Publication Date:  2001 Nov 
Date Detail:
Created Date:  2001-11-23     Completed Date:  2002-01-10     Revised Date:  2009-01-08    
Medline Journal Info:
Nlm Unique ID:  2985121R     Medline TA:  J Biol Chem     Country:  United States    
Other Details:
Languages:  eng     Pagination:  45079-87     Citation Subset:  IM    
Institutes of Biomedical Sciences and Biological Chemistry, Academia Sinica, Taipei 115, Taiwan.
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MeSH Terms
Amino Acid Sequence
Amino Acids / chemistry
Binding Sites
Bungarotoxins / chemistry*,  pharmacology
Chymotrypsin / antagonists & inhibitors*,  chemistry*,  metabolism
Circular Dichroism
Hydrogen Bonding
Magnetic Resonance Spectroscopy
Models, Molecular
Molecular Sequence Data
Multigene Family
Plant Proteins*
Protein Binding
Protein Conformation
Protein Structure, Secondary
Protein Structure, Tertiary
Sequence Homology, Amino Acid
Snake Venoms / chemistry*
Structure-Activity Relationship
Surface Plasmon Resonance
Time Factors
Trypsin Inhibitors / chemistry*
Reg. No./Substance:
0/Amino Acids; 0/BF9 chymotrypsin inhibitor; 0/Bungarotoxins; 0/Disulfides; 0/Kunitz-type protease inhibitor, plant; 0/Peptides; 0/Plant Proteins; 0/Snake Venoms; 0/Trypsin Inhibitors; EC 3.4.21.-/alpha-chymotrypsin; EC

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