Purification, characterization and primary structure of a chymotrypsin inhibitor from Naja atra venom.
A chymotrypsin inhibitor, designated NA-CI, was isolated from the venom of the Chinese cobra Naja atra by three-step chromatography. It inhibited bovine alpha-chymotrypsin with a Ki of 25 nM. The molecular mass of NA-CI was determined to be 6403.8 Da by matrix-assisted laser-desorption ionization time-of-flight (MALDI-TOF) analysis. The complete amino acid sequence was determined after digestion of S-carboxymethylated inhibitor with Staphylococcus aureus V8 protease and porcine trypsin. NA-CI was a single polypeptide chain composed of 57 amino acid residues. The main contact site with the protease (P1) has a Phe, showing the specificity of the inhibitor. NA-CI shared great similarity with the chymotrypsin inhibitor from Naja naja venom (identities=89.5%) and other snake venom protease inhibitors.
Department of Toxinology, Kunming Institute of Zoology, The Chinese Academy of Sciences, 650223 Kunming, Yunnan, PR China.
Xing-Ding
XD
Zhou
Yang
Y
Jin
Qiu-Min
QM
Lu
Dong-Sheng
DS
Li
Shao-Wen
SW
Zhu
Wan-Yu
WY
Wang
Yu-Liang
YL
Xiong
D000595:Amino Acid Sequence; D000818:Animals; D002853:Chromatography, Liquid; D002918:Chymotrypsin / Q000737:chemistry; D004546:Elapid Venoms / Q000737:chemistry*; D017815:Elapidae; D008969:Molecular Sequence Data; D016415:Sequence Alignment; D020539:Sequence Analysis, Protein; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D014361:Trypsin Inhibitors / Q000737:chemistry* / Q000302:isolation & purification*
D004546:Elapid Venoms; D014361:Trypsin Inhibitors; D002918:Chymotrypsin