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[前沿] [生科综合] 热休克蛋白可预防白内障发生

[前沿] [生科综合] 热休克蛋白可预防白内障发生

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热休克蛋白可预防白内障发生
人类眼睛晶状体包含多种高浓度混合蛋白。保护性蛋白能阻止这些蛋白聚合成簇。如果这种保护功能丧失,晶状体就会变得浑浊,病人就会发展为白内障。慕尼黑大学化学院的两个研究组织(TUM)成功的解释了这种保护蛋白的分子结构。

他们发表在在新一期的美国国家科学院的发现,阐明了这些蛋白,可能帮助发展新治疗方案。

细胞中有不同的蛋白复合体(管家蛋白)来完成基本的生命活动。这些分子机制的功能体现依赖于它们的三维立体结构。在一级结构中师长的氨基酸链,像一段长的毛线,在被形成后由被叫做分子伴侣的蛋白帮助折叠成需要的结构。如果折叠过程失败,这些蛋白链就变成卷曲无用。
小的热休克蛋白是分子伴侣中非常重要的一个群体,它们阻止蛋白在应力状态下的聚合。αB晶状体球蛋白和相关的分子伴侣αA晶状体球蛋白是在人体发现的小休克蛋白的主要代表,然而αA晶状体球蛋白主要出现在眼睛的晶状体,αB晶状体球蛋白在脑、心、肌肉组织中很普遍。在眼睛的晶状体中,他们阻碍像白内障等疾病的发生。组织细胞中αB晶状体球蛋白功能障碍能够引起癌症和神经性缺陷病,包括阿尔茨海默氏症。

一些研究机构根据医学相关性把他们的研究重点放在了αA晶状体球蛋白上。尽管足够的努力,直到现在仍然没有给出这些蛋白的分子结构。然而慕尼黑大学的生物化学家现在成功的在细菌研究出αA晶状体球蛋白和αB晶状体球蛋白得重组体,获得了统一、结构清楚的复合物。在该化学部门中心的电镜下进行了这些蛋白的详细结构分析。和以前的假想相比,这个研究组织能够第一次显示,αB晶状体球蛋白由24个亚基组成的球形结构,让人想起穿孔足球。

由于αB晶状体球蛋白三维结构的辨认,现在正在进一步确定,基础成分被建立用来比较健康和引起疾病的突变,依赖于此,进一步澄清他们作用的方式。科学家希望这能够发现新的治疗方法。


http://www.sciencedaily.com/releases/2009/07/090731103328.htm
Heat Shock Proteins Provide Protection Against Cataracts ScienceDaily (Aug. 8, 2009) — The human eye lens consists of a highly concentrated mix of several proteins. Protective proteins prevent these proteins from aggregating and clumping. If this protective function fails, the lens blurs and the patient develops cataracts. Two research groups at the Department of Chemistry of the Technische Universitaet Muenchen (TUM) have succeeded in explaining the molecular architecture of this kind of protective protein.

Their findings, which are published online in the current early edition of PNAS (Proceedings of the National Academy of Sciences), shed new light on the work of these proteins and may be able to help in the development of new treatments.

Cells have a variety of protein complexes that manage vital tasks. The functions of these "molecular machines" depend largely on their three-dimensional structure. In the first instance, proteins are long chains of amino acids, like a long piece of woolen thread. So-called chaperones help them to fold in the desired three-dimensional form after their production. If this folding process fails, the protein thread becomes an inextricable, useless tangle.

Small heat shock proteins (sHsps) are a particularly important group of chaperones. They prevent the clumping of proteins under stress conditions. αB-crystallin and the related sHsp αA-crystallin are the main representatives of the sHsps found in humans. Whereas αA-crystallin mainly occurs in the eye lens, αB-crystallin is also very common in the brain and in the heart and muscle tissue. In the eye lens, they counteract diseases like cataracts. Malfunctions of the αB-crystallin in tissue cells can give rise to cancer and neurological defects, including Alzheimer's disease.

Many research groups have focused their work on the α-crystallins due to their medical relevance. Despite intensive efforts, up to now, none of them have managed to determine the molecular architecture of these proteins. However, TUM biochemists have now succeeded in producing αA-crystallins and αB-crystallins recombinantly in bacteria and in obtaining uniform, clearly-structured complexes. A detailed structural analysis of these proteins was carried out in cooperation with the Chemistry Department's Center of Electron Microscopy. The research groups were able to show for the first time here that, contrary to previous suppositions, αB-crystallin forms a defined globular structure comprising 24 subunits, which are reminiscent of a perforated soccer ball.

Thanks to the identification of the three-dimensional structure of αB-crystallin, which is currently being further refined, the basis has now been established for comparing healthy and disease-promoting mutants and, based on this, for clarifying the way they function. The scientists hope that this will lead to the discovery of new treatments.


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