Liang J N, Chylack L T
Invest Ophthalmol Vis Sci. 1987 May;28(5):790-4.
Nonenzymatic glycated lens alpha-crystallin, isolated from human diabetic cataract lenses, does not differ in subunit size and secondary structure from nonglycated alpha-crystallin. The tertiary structure, however, has undergone a significant change as reflected in the changes of near-ultraviolet (UV) circular dichroism (CD) and fluorescence of intrinsic probes (tryptophan, nontryptophan) and extrinsic probes [(MIANS (6-(4'-maleimidylanilino)naphthalene-2-sulfonic acid) and TNS (6-(p-toluidinyl)naphthalene-2-sulfonate)]. A decrease in tryptophan fluorescence and an increase in nontryptophan fluorescence were observed for glycated alpha-crystallin. Decreased intensities of SH-specific fluorescent probes (MIANS) and hydrophobic probe (TNS) also were observed. The near UV CD and TNS polarization results suggest a more unfolded structure of the glycated crystallin. The significant decrease of sulfhydryl groups in glycated protein suggests that glycation facilitates a further secondary change.
从人类糖尿病性白内障晶状体中分离出的非酶糖化晶状体α-晶体蛋白，其亚基大小和二级结构与未糖化的α-晶体蛋白并无差异。然而，三级结构发生了显著变化，这体现在近紫外（UV）圆二色性（CD）以及内在探针（色氨酸、非色氨酸）和外在探针[（MIANS（6-(4'-马来酰亚胺基苯胺基)萘-2-磺酸）和TNS（6-(对甲苯胺基)萘-2-磺酸盐）]荧光的变化上。对于糖化α-晶体蛋白，观察到色氨酸荧光降低，非色氨酸荧光增加。还观察到SH特异性荧光探针（MIANS）和疏水探针（TNS）的强度降低。近紫外CD和TNS极化结果表明糖化晶体蛋白的结构更加伸展。糖化蛋白中巯基的显著减少表明糖基化促进了进一步的二级结构变化。
