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The oxidative folding of disulfide-rich conotoxins is essential for their biological functions.In vivo, disulfide bond formation is mainly catalyzed by protein disulfide isomerase. To elucidate the physiologic roles of pro-tein disulfide isomerase in the folding of conotoxins, we have cloned a novel full-length protein disulfide isomerase from Conus marmoreus. | ễFEBS Journal Molecular cloning expression and characterization of protein disulfide isomerase from Conus marmoreus Zhi-Qiang Wang1 Yu-Hong Han1 2 Xiao-Xia Shao1 Cheng-Wu Chi1 2 and Zhan-Yun Guo1 1 Institute of Protein Research Tongji University Shanghai China 2 Institute of Biochemistry and Cell Biology Shanghai Institutes for BiologicalSciences Chinese Academy of Sciences Graduate Schoolof the Chinese Academy of Sciences Shanghai China Keywords conotoxin disulfide isomerization oxidative folding protein disulfide isomerase Correspondence Z.-Y. Guo Institute of Protein Research Tongji University 1239 Siping Road Shanghai 200092 China Fax 86 21 65988403 Tel 86 21 65985167 E-mail zhan-yun.guo@mail.tongji.edu.cn C.-W. Chi Shanghai Institute of Biochemistry and Cell Biology Chinese Academy of Sciences 320 YueYang Road Shanghai 200031 China Fax 86 21 54921011 Tel 86 21 54921165 E-mail chi@sunm.shcnc.ac.cn Received 2 March 2007 revised 8 July 2007 accepted 18 July 2007 The oxidative folding of disulfide-rich conotoxins is essential for their biological functions. In vivo disulfide bond formation is mainly catalyzed by protein disulfide isomerase. To elucidate the physiologic roles of protein disulfide isomerase in the folding of conotoxins we have cloned a novel full-length protein disulfide isomerase from Conus marmoreus. Its ORF encodes a 500 amino acid protein that shares sequence homology with protein disulfide isomerases from other species and 70 homology with human protein disulfide isomerase. Enzymatic analyses of recombinant C. marmoreus protein disulfide isomerase showed that it shared functional similarities with human protein disulfide isomerase. Using conotoxins tx3a and sTx3.1 as substrate we analyzed the oxidase and isomerase activities of the C. marmoreus protein disulfide isomerase and found that it was much more efficient than glutathione in catalyzing oxidative folding and disulfide isomerization of conotoxins. We further demonstrated that .
