Center for Integrated Protein Science Munich, Chemistry Department, Technische Universität München, Lichtenbergstrasse 4, 85747 Garching, Germany.
Proc Natl Acad Sci U S A. 2011 Dec 20;108(51):20491-6. doi: 10.1073/pnas.1111014108. Epub 2011 Dec 5.
The molecular chaperone αB-crystallin, the major player in maintaining the transparency of the eye lens, prevents stress-damaged and aging lens proteins from aggregation. In nonlenticular cells, it is involved in various neurological diseases, diabetes, and cancer. Given its structural plasticity and dynamics, structure analysis of αB-crystallin presented hitherto a formidable challenge. Here we present a pseudoatomic model of a 24-meric αB-crystallin assembly obtained by a triple hybrid approach combining data from cryoelectron microscopy, NMR spectroscopy, and structural modeling. The model, confirmed by cross-linking and mass spectrometry, shows that the subunits interact within the oligomer in different, defined conformations. We further present the molecular architectures of additional well-defined αB-crystallin assemblies with larger or smaller numbers of subunits, provide the mechanism how "heterogeneity" is achieved by a small set of defined structural variations, and analyze the factors modulating the oligomer equilibrium of αB-crystallin and thus its chaperone activity.
分子伴侣αB-晶状体蛋白是维持眼睛晶状体透明度的主要参与者，可防止应激损伤和衰老的晶状体蛋白聚集。在非晶状体细胞中，它与各种神经疾病、糖尿病和癌症有关。鉴于其结构的灵活性和动态性，迄今为止，αB-晶状体蛋白的结构分析一直是一个艰巨的挑战。在这里，我们通过结合电子显微镜、NMR 光谱和结构建模数据的三重杂交方法，提出了一个 24 聚体αB-晶状体蛋白组装体的拟原子模型。该模型通过交联和质谱得到了验证，表明亚基在低聚物中以不同的、确定的构象相互作用。我们进一步展示了更多具有更大或更小亚基数目的αB-晶状体蛋白组装体的分子结构，提供了通过一小部分定义的结构变化实现“异质性”的机制，并分析了调节αB-晶状体蛋白低聚物平衡及其伴侣活性的因素。
