Molecular Structure and Function of Crystallins

在人类和动物模型中，γ-晶体蛋白与白内障相关。它们也可能在其他眼组织中具有与压力相关的作用，特别是视网膜。我们已经证明它们在透镜的细胞骨架稳定中起作用。 g-晶体蛋白具有非常不寻常的溶液性质，适合高蛋白浓度环境。 它们具有稳定的、紧密折叠的结构，但可以展开形成淀粉样原纤维。我们已经研究了展开/重折叠的GS-晶体蛋白家族的成员从鸟类和哺乳动物。鸟类和哺乳动物之间不同的单个氨基酸残基似乎在确定蛋白质折叠的长期稳定性和蛋白质采用似乎抵抗光散射聚集体形成的替代构象的能力中具有关键作用。 我们已经结晶并解决了鸡GS-晶体蛋白的三维结构，第一个GS被结晶。我们已经发现结晶依赖于鸟类特有的不寻常的L16残基。该残基也影响分子间相互作用的其它重要方面。晶体结构揭示了一种意想不到的gS二聚模式。特别地，该单体蛋白形成在取向上与β-晶体蛋白中的二聚化界面相同的晶格接触（QR）。我们发现，采用QR接口的蛋白质表现出加性分子偶极子，这表明一个重要的机制，协会的晶体蛋白。晶体结构还显示了单体γ-晶体蛋白如何从多聚体β-晶体蛋白产生，以及γ-晶体蛋白如何能够与仅一层紧密结合的结合水形成非常紧密的非结合蛋白质接触，这是对眼睛透镜的分子拥挤的明显适应。 此外，我们已经结晶了小鼠gS的变体，揭示了一个显着的结构，似乎是一个聚集中间体，涉及分子内和分子间的S-S键，应变结构域交换和二级结构的渐进损失。这增加了对导致白内障的过程的重要见解。 我们还获得了先前未溶解的β晶体蛋白的晶体，包括异源二聚体。

gamma-Crystallins are associated with cataract in both human and animal models. They may also have stress related roles in other eye tissues, notably retina. We have shown that they can play a role in stabilization of cytoskeleton in lens. g-Crystallins have highly unusual solution properties that fit them for high protein concentration environments. They have stable, tightly folded structures but can unfold to form amyloid like fibrils. We have studied unfolding/refolding in members of the gS-crystallin family from birds and mammals. A single amino acid residue which differs between birds and mammals appears to have a key role in determining long term stability of the protein fold and the ability of the protein to adopt an alternative conformation which seems to resist formation of light scattering aggregates. We have crystallized and solved the three-dimensional structure of chicken gS-crystallin, the first gS to be crystallized. We have found that crystallization is dependent on the unusual L16 residue specific to birds. this residue also affects other important aspects of intermolecular interactions.the crystal structure reveals an unexpected mode for gS dimerization. In particular this monomeric protein forms a crystal lattice contact (QR)identical in orientation to the dimerization interface in beta-crystallins. We show that proteins adopting the QR interface exhibit additive molecule dipoles, which suggests an important mechanism for association of crystallins. The crystal structure also shows how monomeric gamma-crystallins arose from multimeric beta-crystallins and how gamma-crystallins are able to form very close, non-binding protein contacts with just a thin layer of tightly bound bound water, a clear adaptation for the molecular crowing of the eye lens. In addition we have crystallized a variant of mouse gS, revealing a remarkable structure that appears to be an aggregation intermediate involving intra- and inter-molecular S-S bonds, strained domain swapping and prgressive loss of secondary srtucture. This adds important insight into the processes that lead to cataract. We have also obtained crystals for previously unsolved beta crystallins, including a heterodimer.