title: Investigation of the structural stability of cardiotoxin analogue III from the Taiwan cobra by hydrogen-deuterium exchange kinetics.
abstract: The conformational stability of a small ( approximately 7 kDa), all beta-sheet protein, cardiotoxin analogue III (CTX III), from the venom of the Taiwan cobra has been investigated by hydrogen-deuterium (H/D) exchange using two-dimensional NMR spectroscopy. The H/D exchange kinetics of backbone amide protons in CTX III has been monitored at pD 3.6 and 6.6 (at 25 degrees C), for over 5000 h. Examination of H/D exchange kinetics in the protein showed that a number of slowly exchanging residues are in the hydrophobic core of the protein. The average protection factor of the amide protons of residues belonging to the triple-stranded beta-sheet domain is about 20 times greater than that of those in the double-stranded beta-sheet segment. The residues in the C-terminal tail of the molecule, though structureless, have been found to exhibit significant protection against H/D exchange. Comparison of the quenched-flow H/D exchange data on CTX III with those obtained in the present study reveals that the most slowly exchanging portion constitutes the folding core of the protein.
authors.affiliation: Department of Chemistry, National Tsing Hua University, Hsinchu, Taiwan.
authors.forename: T
authors.initials: T
authors.lastname: Sivaraman
authors.forename: T K
authors.initials: TK
authors.lastname: Kumar
authors.forename: C
authors.initials: C
authors.lastname: Yu
mesh_terms: D000577:Amides / Q000737:chemistry; D000596:Amino Acids / Q000737:chemistry; D000818:Animals; D004179:Cobra Cardiotoxin Proteins / Q000737:chemistry*; D017666:Deuterium Oxide / Q000737:chemistry*; D019791:Guanidine; D007700:Kinetics; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular; D011487:Protein Conformation; D011489:Protein Denaturation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D011522:Protons
chemical_list: D000577:Amides; D000596:Amino Acids; D004179:Cobra Cardiotoxin Proteins; D011522:Protons; C082202:cardiotoxin III, Naja naja atra; D017666:Deuterium Oxide; D019791:Guanidine