The effects of aspartic acid-bond isomerization on in vitro properties of the amyloid beta-peptide as modeled with N-terminal decapeptide fragments.
The effects of aspartic acid-bond isomerization on in vitro properties of the amyloid beta-peptide as modeled with N-terminal decapeptide fragments.
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天冬氨酸键异构化对淀粉样β-肽体外特性的影响（以 N 端十肽片段为模型）。
DOI：
10.1111/j.1399-3011.1996.tb01358.x
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发表时间：
1996
期刊：
影响因子：
--
通讯作者：
OtvosJr,L
中科院分区：
文献类型：
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作者：
Szendrei,GI;Prammer,KV;Vasko,M;Lee,VM;OtvosJr,L
由42个氨基酸组成的A-β是阿尔茨海默病患者脑内老年斑沉积的主要成分，其N-末端具有高度的异质性。活体和体外研究表明，残基1和7上的天冬氨酸键的异构化使Aβ更容易聚集并形成延伸结构。我们最近用CD证明了中链天冬氨酸键异构化能够破坏末端十肽片段的优势螺旋结构。在目前的研究中，我们使用分子模拟来表明额外的CH2-基团插入到十肽骨架中会导致稳定的反转形成，并破坏在全尺寸肽水平上与延伸结构竞争的螺旋构象的稳定。分子模拟还揭示了二异构化肽直接形成延伸结构的有限倾向。抗A-βPAb2332对十肽的非异构化状态比全长多肽更敏感。针对未修饰的Aβ的单抗6E10以构象依赖的方式仅识别未修饰的十肽或在第一天冬氨酸异构化的肽，但在任何情况下都不识别中链异构化或二异构化的十肽。用二异构化的十肽作为免疫原，制备多克隆抗体14943，该抗体对全长多肽或十肽的异构化状态都不具有选择性，但在酶联免疫分析过程中当多肽抗原结构保守时，优先识别异构化的多肽。由于全尺寸A-β多肽在标准反相高效液相中的异常行为，可以更有效地对十肽片段进行表明细胞外稳定性的血清稳定性研究。值得注意的是，与未修饰或单异构化的多肽相比，二异构化的多肽对血清多肽酶的稳定性显著提高，这可能是异构化的Aβ多肽在脑内滞留的可能机制。孟克斯加德1996年。
The 42‐amino acid Aβ, the major constituent of the senile plaque deposits of the brains of Alzheimer's disease patients, exhibits a high degree of heterogeneity at itsN‐terminus. Isomerization of aspartic acid bonds at residues 1 and 7 renders Aβ more prone to aggregate and form extended structure as it was shown byin vivoandin vitrostudies. We recently demonstrated the ability of mid‐chain aspartic acid‐bond isomerization to break the dominant helical structure of theN‐terminal decapeptide fragment by CD. In the current study we use molecular modeling to show that insertion of the extra ‐CH2‐group into the decapeptide backbone results in the formation of stable reverse‐turns and destabilizes the helical conformer that competes with the extended structure at the full‐sized peptide level. The molecular modeling also reveals a limited propensity of the diisomerized peptide to form extended structure directly. Anti‐Aβ pAb 2332 is more sensitive for the non‐isomerized status of the decapeptide than that of the full‐sized peptide. mAb 6E10, raised against unmodified Aβ recognizes only the unmodified decapeptide or the peptide isomerized at the first aspartic acid in a conformation‐dependent manner, but does not recognize the mid‐chain isomerized or diisomerized decapeptide in any circumstance. The diisomerized decapeptide was used as immunogen to generate polyclonal antibody 14943 that is not selective for the isomerized status of either the full‐size peptide or the decapeptide, but recognizes the isomerized peptides preferentially when the peptide antigen structures are conserved during the enzyme‐linked immunoassay procedure. Owing to the aberrant behavior of the full‐sized Aβ peptide during standard RP‐HPLC, serum stability studies that indicate extracellular stability can be more effectively performed on the decapeptide fragments. Remarkably, the diisomerized peptide exhibits a significantly increased stability towards serum peptidases compared with the unmodified or monoisomerized peptides, suggesting a possible mechanism of the retention of the isomerized Aβ peptide in the affected brains. © Munksgaard 1996.