Probing the structure and interactions of crystallin proteins by NMR spectroscopy
Probing the structure and interactions of crystallin proteins by NMR spectroscopy
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DOI：
10.1016/s1350-9462(98)00027-5
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发表时间：
1999-07-01
影响因子：
17.8
通讯作者：
Carver, JA
中科院分区：
文献类型：
--
作者：
Carver, JA
晶状体主要由蛋白质组成，即晶体蛋白，它们的结构和相互作用决定了晶状体的透明度。由于大多数晶状体中没有蛋白质周转，晶体蛋白必须是非常稳定和长寿的蛋白质。晶体蛋白有三种类型：α、β和α，它们都是由各种亚基组成的。此外，许多亚基都经历了广泛的翻译后修饰。确定晶状体中晶体蛋白的结构特征和优先相互作用和结合是一项庞大而复杂的实验工作。通过x射线晶体学对β -和γ -晶体蛋白的代表性结构的测定，在这一领域取得了一些进展[Slingsby， C, Norledge， B., Simpson， A., Bateman， O. A., Wright， G., Driessen h.p. C., Lindley， P. F., Moss， D. S.和Bar]。B.（1997）晶体蛋白的x射线衍射和结构。掠夺。[j].中华眼科杂志，2016,33(3):391 - 391。本文综述了核磁共振（NMR）测定晶体蛋白这些方面信息的方法。结果表明，尽管它们的尺寸相对较大，但所有的结晶蛋白都产生了分辨率很高的核磁共振光谱，这些核磁共振光谱来自于从蛋白质结构域核心延伸出来的柔性末端延伸。通过检查不同晶体蛋白亚基混合物的核磁共振光谱，可以确定这些延伸在晶体-晶体蛋白相互作用中的作用。例如，两个α -结晶蛋白亚基中的柔性c端延伸不参与与其他结晶蛋白的相互作用，但在α -结晶蛋白的伴侣作用中至关重要。在这种作用下，α -结晶蛋白在压力条件下稳定其他蛋白质，例如热。在晶状体中，这种能力可能在防止晶状体蛋白随着年龄的增长而沉淀，从而促进白内障的形成方面具有重要的作用。α -结晶蛋白的c端延伸作为蛋白质和高分子量复合物的增溶剂，这种复合物是在与沉淀的“底物”蛋白质的伴侣作用下形成的。在与α -结晶蛋白有关的各种小热休克蛋白中也观察到类似的行为。核磁共振研究也与α -结晶蛋白的双畴结构相一致。α -结晶蛋白没有晶体结构。利用核磁共振数据，提出了α -晶体蛋白的四元结构模型，该模型包括环状排列的亚基和一个大的中心空腔。1999爱思唯尔科学有限公司版权所有。
The lens is composed primarily of proteins, the crystallins, at high concentration whose structure and interactions are responsible for lens transparency. As there is no protein turnover in the majority of the lens, crystallin proteins have to be very stable and long-lived proteins. There are three types of crystallin proteins: alpha, beta and gamma, and they all are composed of a variety of subunits. In addition, extensive post-translational modification is undergone by many of the subunits. Determining the structural features and the preferential interactions and associations undergone by the crystallin proteins in the lens is a large and complex experimental undertaking. Some progress has been made in this area by X-ray crystallographic determination of structures for representative examples of the beta- and gamma-crystallins [Slingsby, C., Norledge, B., Simpson, A., Bateman, O. A., Wright, G., Driessen H. P. C., Lindley, P. F., Moss, D. S. and Bar. B. (1997) X-ray diffraction and structure of crystallins. Prog. Ret. Eye Res. 16, 3-29]. In this article, a summary is given of nuclear magnetic resonance (NMR) methods to determine information about these aspects of crystallin proteins. It is shown that despite their relatively large size, all crystallins give rise to well-resolved NMR spectra which arise from flexible terminal extensions that extend from the domain core of the proteins. By examining NMR spectra of mixtures of different crystallin subunits, it is possible to determine the role of these extensions in crystallin-crystallin interactions. For example, the flexible C-terminal extensions in the two alpha-crystallin subunits are not involved in interacting with the other crystallins but are crucially important in the chaperone action of alpha-crystallin. In this action, alpha-crystallin stabilises other proteins under conditions of stress, e.g. heat. In the lens, this ability probably has important consequences in preventing the precipitation of crystallin proteins with age and thereby contributing to cataract formation. The C-terminal extensions in alpha-crystallin act as solubilising agents for the protein and the high-molecular-weight complex that forms upon chaperone action with a precipitating "substrate" protein. Similar behaviour is observed for a variety of small heat-shock proteins, to which alpha-crystallin is related. NMR studies are also consistent with a two-domain structure for alpha-crystallin. No crystal structure is available for alpha-crystallin. Using the NMR data, a model for the quaternary structure of alpha-crystallin is proposed which comprises an annular arrangement for the subunits with a large central cavity. (C) 1999 Elsevier Science Ltd. All rights reserved.