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Free tyrosine and tyrosine-rich peptide-dependent superoxide generation catalyzed by a copper-binding, threonine-rich neurotoxic peptide derived from prion protein

机译：由from病毒蛋白衍生的铜结合，富含苏氨酸的神经毒性肽催化游离酪氨酸和富含酪氨酸的肽依赖性超氧化物的产生

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Previously, generation of superoxide anion (O2•-) catalyzed by Cu-binding peptides derived from human prion protein (model sequence for helical Cu-binding motif VNITKQHTVTTTT was most active) in the presence of catecholamines and related aromatic monoamines such as phenylethylamine and tyramine, has been reported [Kawano, T., Int J Biol Sci 2007; 3: 57-63]. The peptide sequence (corresponding to helix 2) tested here is known as threonine-rich neurotoxic peptide. In the present article, the redox behaviors of aromatic monoamines, 20 amino acids and prion-derived tyrosine-rich peptide sequences were compared as putative targets of the oxidative reactions mediated with the threonine-rich prion-peptide. For detection of O2•-, an O2•--specific chemiluminescence probe, Cypridina luciferin analog was used. We found that an aromatic amino acid, tyrosine (structurally similar to tyramine) behaves as one of the best substrates for the O2•- generating reaction (conversion from hydrogen peroxide) catalyzed by Cu-bound prion helical peptide. Data suggested that phenolic moiety is required to be an active substrate while the presence of neither carboxyl group nor amino group was necessarily required. In addition to the action of free tyrosine, effect of two tyrosine-rich peptide sequences YYR and DYEDRYYRENMHR found in human prion corresponding to the tyrosine-rich region was tested as putative substrates for the threonine-rich neurotoxic peptide. YYR motif (found twice in the Y-rich region) showed 2- to 3-fold higher activity compared to free tyrosine. Comparison of Y-rich sequence consisted of 13 amino acids and its Y-to-F substitution mutant sequence revealed that the tyrosine-residues on Y-rich peptide derived from prion may contribute to the higher production of O2•-. These data suggest that the tyrosine residues on prion molecules could be additional targets of the prion-mediated reactions through intra- or inter-molecular interactions. Lastly, possible mechanism of O2•- generation and the impacts of such self-redox events on the conformational changes in prion are discussed.
机译：以前，在儿茶酚胺和相关的芳族单胺（如苯乙胺和酪胺）存在下，由人protein病毒蛋白衍生的Cu结合肽（螺旋铜结合基序VNITKQHTVTTTT的模型序列最活跃）催化生成超氧阴离子（O2•-）。 ，已被报道[Kawano，T.，Int J Biol Sci 2007； J.Biol.Sci。，2007； 5：1593-63。 3：57-63]。在此测试的肽序列（对应于螺旋2）被称为富含苏氨酸的神经毒性肽。在本文中，比较了芳香族单胺，20个氨基酸和富含病毒的酪氨酸肽序列的氧化还原行为，将其作为由富含苏氨酸的ion病毒肽介导的氧化反应的假定靶标。为了检测O2•-（一种O2•-特异性化学发光探针），使用了Cypridina luciferin类似物。我们发现，一种芳香族氨基酸酪氨酸（结构上类似于酪胺）是铜结合的ion病毒螺旋肽催化的O2•生成反应（由过氧化氢转化）的最佳底物之一。数据表明，酚部分必须是活性底物，而羧基和氨基都不需要存在。除了游离酪氨酸的作用外，还测试了在人类病毒中发现的两个富含酪氨酸的肽序列YYR和DYEDRYYRENMHR（与富含酪氨酸的区域相对应）作为富含苏氨酸的神经毒性肽的假定底物的作用。与游离酪氨酸相比，YYR基序（在富Y区域中发现两次）显示出高出2到3倍的活性。富Y序列由13个氨基酸组成，其Y到F取代突变序列的比较表明，on病毒衍生的富Y肽上的酪氨酸残基可能有助于产生更高的O2•-。这些数据表明蛋白分子上的酪氨酸残基可能通过分子内或分子间相互作用成为additional蛋白介导的反应的其他靶标。最后，讨论了O2•生成的可能机理以及此类自氧化还原事件对pr病毒构象变化的影响。

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