老化・紫外線・放射線によるタンパク質中のD-β-アスパラギン酸生成とその機構

I）正常晶状体中人α A-晶状体蛋白中ASP-151和ASP-58残留物的转化和异构化。虽然蛋白质通常完全由L-氨基酸组成，但我们发现，在老化过程中，来自老年人透镜的α A-晶状体蛋白中的Asp-151和Asp-58被转化为生物学上不常见的D-β-异构体。剧烈的变化开始于出生时，大约45%的正常L-α-天冬氨酸失去了30年的范围。Asp残基的这些修饰可能影响透镜蛋白的三维堆积阵列。II）γ-辐照α-晶体蛋白的伴侣蛋白样活性丧失与氧化、异构化和外消旋化之间的相关性。α-晶状体蛋白具有防止蛋白质聚集的分子伴侣样活性;然而，这种活性的机制尚不清楚。在这里，我们有γ射线照射的α-晶状体蛋白，并研究了分子伴侣样活性的降低与修饰的α-晶状体蛋白之间的关系。 ...更多信息 在该分子中氨基酸的氧化、异构化和外消旋化。我们发现α-晶状体蛋白的分子伴侣样活性随着γ射线照射的增加而降低。照射的α-晶状体蛋白的二级结构没有改变，但是其三级结构的α-晶状体蛋白似乎改变超过1000 Gy的照射。根据辐射剂量，α A-晶状体蛋白的Met- 1被氧化为甲硫氨酸亚砜。此外，照射后α A-晶状体蛋白的Asp-151异构化为β-Asp形式，并且Asp-151的外消旋化减少。因此，α-晶状体蛋白的铁分子伴侣样活性的丧失与其异构化、氧化和外消旋化的变化有关。III）生物学上不常见的在太阳损伤皮肤的弹性纤维中的含D-β-天冬氨酸蛋白。我们制备了抗D-β-Asp蛋白的抗体，并检测了其在皮肤中的免疫反应性。这种抗体识别暴露在阳光下的皮肤中分解的弹性纤维。Western免疫印迹分析表明，该多肽分子量为50 kDa，能与D-β-Asp蛋白和弹性蛋白抗体发生免疫反应。这一结果表明，紫外线照射后弹性纤维蛋白中的天冬氨酸残基发生了明显的外消旋和异构化，在老化过程中积累了异常蛋白。我们建议，该抗体可能是一个有用的指标，为阳光损害的皮肤。少

I) INVERSION AND ISOMERIZATION OF ASP-151 AND ASP-58 RESIDUE IN HUMAN ALPHA A-CRYSTALLIN FROM NORMALAGED LENSES. Although proteins are generally composed entirely of L-amino acids, we showed that Asp-151 and Asp-58 in alpha A-crystallin from aged human lens is inverted to the biologically uncommon D-beta-isomer to a high degree during aging. The drastic changes started at birth, with about 45 % of normal L- alpha -Asp lost by the 30 year range. These modifications of the Asp residue likely affects the three-dimensional packing array of the lens proteins.II) CORRELATION BETWEEN LOSS OF CHAPERONE-LIKE ACTIVITY, AND OXIDATION, ISOMERIZATION AND RACEMIZATION OF GAMMA-IRRADIATED ALPHA-CRYSTALLIN. Alpha-crystallin possesses a molecular chaperone-like activity that prevents proteins from aggregating ; however, the mechanism of this activity is not well known. Here we have gamma-irradiated alpha-crystallin and studied the relationship between the decrease in chaperone-like activity and modific … More ations such as oxidation, isomerization and racemization of amino acids in this molecule. We found that the chaperone-like activity of alpha-crystallin decreased with increasing gamma irradiation. The secondary structure of the irradiated alpha-crystallin did not change, however its tertiary structure of the alpha-crystallin seems to change more than 1000Gy irradiation. Depending on the radiation dose, Met- 1 of alpha A-crystallin was oxidized to methionine sulfoxide. In addition, Asp-151 of alpha A-crystallin was isomerized to the beta-Asp form after irradiation, and racemization of Asp-151 was decreased. Thus, loss of the fe chaperone-like activity of alpha-crystallin is related to changes in its isomerization, oxidation and racemization.III) BIOLOGICALLY UNCOMMON D-BETA-ASPARTIC ACID-CONTAINING PROTEIN IN ELASTIC FIBERS OF SUN DAMAGED SKIN. We have prepared the antibody agaist D-beta-Asp containing protein and examined its immunoreactivity in skin. The antibody recognized disintegrated elastic fibers in sun-exposed skin. Western plot analysis of the proteins isolated from sun-damaged skin demonstrated that the polypeptide with 50kDa was immunoreactive with the antibodies for D-beta-Asp containing protein and elastin. This result suggests that UV irradiation significant racemization and isomerization of Asp resideus in proteins of elastic fibers and the unusual proteins were accumulated during aging. We propose that the antibody could be a useful indicator for sun damage of the skin. Less