Events in the kinetic folding pathway of a small, all beta-sheet protein.
The folding of cardiotoxin analogue III (CTX III), a small (60 amino acids), all beta-sheet protein from the venom of the Taiwan Cobra (Naja naja atra) is here investigated. The folding kinetics is monitored by using a variety of techniques such as NMR, fluorescence, and circular dichroism spectroscopy. The folding of the protein is complete within a time scale of 200 ms. The earliest detectable event in the folding pathway of CTX III is the formation of a hydrophobic cluster, which possess strong affinity to bind to nonpolar dye such as 1-anilino-8-napthalene-sulfonic acid. Quenched-flow deuterium-hydrogen exchange experiments indicate that the segment spanning residues 51-55 along with Lys23, Ile39, Val49, Tyr51 and Val52 could constitute the "hydrophobic cluster." Folding kinetics of CTX III based on the amide-protection data reveals that the triple-stranded, antiparallel beta-sheet segment, which is located in the central core of the molecule, appears to fold faster than the double-stranded beta-sheet segment.
Sivaraman
T
T
Department of Chemistry, National Tsing Hua University, Hsinchu, 300 Taiwan.
Kumar
T K
TK
Chang
D K
DK
Lin
W Y
WY
Yu
C
C
D000577:Amides / Q000737:chemistry; D002942:Circular Dichroism; D004179:Cobra Cardiotoxin Proteins / Q000737:chemistry*; D004546:Elapid Venoms / Q000737:chemistry*; D007700:Kinetics; D008956:Models, Chemical; D017510:Protein Folding; D013056:Spectrophotometry, Ultraviolet
D000577:Amides; D004179:Cobra Cardiotoxin Proteins; D004546:Elapid Venoms; C082202:cardiotoxin III, Naja naja atra