Phthalocyanine tetrasulfonates bind to multiple sites on natively-folded prion protein

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• 作者：Derek R. Dee^a ; ¹ ; Amar Nath Gupta^a ; ¹ ; Max Anikovskiy^b ; Iveta Sosova^c ; Elena Grandi^a ; Laura Rivera^a ; Abhilash Vincent^a ; Angela M. Brigley^c ; Nils O. Petersen^b ; ^c ; Michael T. Woodside^a ; ^c ; ^{Michael.Woodside@nrc-cnrc.gc.ca}
• 关键词：PcTS ; phthalocyanine tetrasulfonate ; FB-PcTS ; free-base-phthalocyanine tetrasulfonate ; PrPC ; natively-folded prion protein ; PrPSc ; misfolded ; disease-related prion protein ; SPR ; surface plasmon resonance ; ITC ; isothermal titration calorimetry ; FCS ; fluore
• 刊名：Biochimica et Biophysica Acta - Proteins and Proteomics
• 出版年：2012
• 期刊代码：161_15709639
• 类别：bio
• 出版时间：June, 2012
• 卷：1824
• 期：6
• 页码：826-832
• 文件大小：888 K

摘要

The phthalocyanine tetrasulfonates (PcTS), a class of cyclic tetrapyrroles, bind to the mammalian prion protein, PrP. Remarkably, they can act as anti-scrapie agents to prevent the formation and spread of infectious, misfolded PrP. While the effects of phthalocyanines on the diseased state have been investigated, the interaction between PcTS and PrP has not yet been extensively characterized. Here we use multiple, complementary assays (surface plasmon resonance, isothermal titration calorimetry, fluorescence correlation spectroscopy, and tryptophan fluorescence quenching) to characterize the binding of PcTS to natively-folded hamster PrP(90-232), in order to determine binding constants, ligand stoichiometry, influence of buffer ionic strength, and the effects of chelated metal ions. We found that binding strength depends strongly on chelated metal ions, with Al^3 +-PcTS binding the weakest and free-base PcTS the strongest of the three types tested (Al^3 +, Zn^2 +, and free-base). Buffer ionic strength also affected the binding, with K_d increasing along with salt concentration. The binding isotherms indicated the presence of at least two different binding sites with micromolar affinities and a total stoichiometry of ~ 4-5 PcTS molecules per PrP molecule.