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首页> 外文期刊>Biochemistry >Stereospecific Amyloid-like Fibril Formation by a Peptide Fragment of beta_2-Microglobulin
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Stereospecific Amyloid-like Fibril Formation by a Peptide Fragment of beta_2-Microglobulin

机译：β_2微球蛋白的肽片段的立体特异性淀粉样样原纤维形成。

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Understanding the role of the L/D-stereospecificity of amino acids is important in obtaining further insight into the mechanism of the formation of amyloid fibrils.beta_2-Microglobulin is a major component of amyloid fibrils deposited in patients with dialysis-related amyloidosis.A 22-residue peptide of beta_2-microglobulin,Ser20-Lys41 (L-K3 peptide),obtained by digestion with Acromobacter protease I,formed amyloid-like fibrils in 50% (v/v) 2,2,2-trifluoroethanol and 10 mM HC1 at 25 deg C,as confirmed by thioflavin T fluorescence,circular dichroism spectra,and atomic force microscopy images.A synthetic K3 peptide composed of D-amino acids (D-K3 peptide) formed similar fibrils but with opposite chirality as indicated by circular dichroism spectra.A mixture of L-K3 and D-K3 peptides also formed fibrils,although the L- and D-amino acid composition of each fibril is unknown.To examine the possible cross-reactivity between L- and D-enantiomers,we carried out seeding experiments in which preformed seeds were extended by monomers.The results revealed that only the homologous extensions proceed smoothly,i.e.,the growth of L-seeds by L-monomers or D-seeds by D-monomers.The results suggest that,while the fibrils derived from L- and D-peptides form in a similar manner but with opposite stereochemistry,a cross-reaction between them is prevented because the geometry of the mixed sheet cannot satisfy dominant factors for beta-sheet stabilization.
机译：了解氨基酸的L / D-立体特异性的作用对于进一步了解淀粉样蛋白原纤维的形成机理很重要.β_2-微球蛋白是透析相关淀粉样变性患者沉积的淀粉样蛋白原纤维的主要成分.A 22 β-微球蛋白的S-残基肽Ser20-Lys41（L-K3肽），通过Acromobacter蛋白酶I消化获得，在50％（v / v）2,2,2-三氟乙醇和10 mM HCl中形成淀粉样原纤维。硫代黄素T荧光，圆二色光谱和原子力显微镜图像证实，在25摄氏度下，由D-氨基酸组成的合成K3肽（D-K3肽）形成相似的原纤维，但圆二色性表明其手性相反L-K3和D-K3肽的混合物也形成了原纤维，尽管每个原纤维的L-和D-氨基酸组成都是未知的。为了研究L-和D-对映异构体之间可能的交叉反应性，我们进行了分析。进行播种实验，其中预结果表明，只有同源的延伸才能顺利进行，即L-单体通过L-单体的生长或D-种子通过D-单体的生长。结果表明，原纤维衍生自L -和D-肽以相似的方式形成，但是具有相反的立体化学，由于混合片层的几何形状不能满足β-片层稳定的主导因素，因此防止了它们之间的交叉反应。

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