|Purification and Crystallization of Natrin, a Cystein-rich Secretory Protein, from Naja atra
Yu-Lin Wang (王玉玲)1,2, Shao-Chen Lee (李紹楨)2, King-Xiang Goh (吳欽祥)2,
Wen-guey Wu (吳文桂)2, and Chun-Jung Chen (陳俊榮)1
1 Structural Biology Group, National Synchrotron Radiation Research Center, Hsinchu, Taiwan
2 Institute of Bioinformatics and Structural Biology, National Tsing-Hua University, Hsinchu, Taiwan
Cysteine-rich secretory proteins (CRISPs) may play a role in the innate immune system and are transcriptionally regulated by androgens in several tissues. They are mostly found in epididymis and granules of mammals . A number of snake venoms, from habu snake, erabu sea snake, Conus textile, etc., contain CRISP family proteins  . Natrin has a cysteine-rich C-terminal tail and belongs to a family of CRISPs. We have purified the natrin protein from Naja atra (Taiwan cobra) venom using a three-step chromatography procedure. The protein is composed of 239 amino acid residues, which has an apparent molecular mass of 24941 Da with an alkaline pI value of 8.5 and consists of one single polypeptide chain as estimated by mass spectrometry and SDS-PAGE.
The biological function of natrin is unclear so far. We have obtained natrin crystals and tend to determine the structural by X-ray crystallography to understand its special biological function in venom. The purification and preliminary X-ray analysis will be discussed.
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