Tardieu A
Systèmes Moléculaires et Biologie Structurale, LMCP, URA 09 CNRS-Universités Paris 6 et 7, France.
Int J Biol Macromol. 1998 May-Jun;22(3-4):211-7. doi: 10.1016/s0141-8130(98)00018-x.
The eye lens is the foremost biological system where function is directly under control of the physico-chemical properties of the cytoplasmic macromolecular solution. Indeed, lens transparency and opacity, lens refractive index gradient and viscosity, are the result of the structural and interactive properties of the crystallins, of their stability, of the fine tuning of their interaction potentials and associations at different levels of organization. Among the different crystallin classes, alpha-crystallins have represented a major challenge for a long time. The alpha-crystallin secondary, tertiary and quaternary structures are still unknown. On the functional side, however, it is established that alpha-crystallin quaternary structure and repulsive interactions determine lens transparency, whereas the alpha-crystallin chaperone effect most probably plays a role in the aging process. In the present paper, we recall the physico-chemical properties and the quaternary structure features of alpha-crystallins that were demonstrated to control light scattering and transparency. The interest of a crystallin mixture for lens function is discussed. Then, a formal approach is proposed to design models for the alpha-crystallin quaternary structure, including the question of whether alpha-crystallins assemble with symmetry. An hypothesis relevant to the fold of the alpha-crystallin C-terminal domain is presented in another paper in this issue.
眼球晶状体是最重要的生物系统，其功能直接受细胞质大分子溶液物理化学性质的控制。事实上，晶状体的透明度与不透明度、晶状体折射率梯度和粘度，都是晶状体蛋白的结构和相互作用特性、它们的稳定性、以及在不同组织层次上其相互作用势和缔合的精细调节的结果。在不同种类的晶状体蛋白中，α-晶状体蛋白长期以来一直是一个重大挑战。α-晶状体蛋白的二级、三级和四级结构仍然未知。然而，在功能方面，已经确定α-晶状体蛋白的四级结构和排斥相互作用决定了晶状体的透明度，而α-晶状体蛋白的伴侣效应很可能在衰老过程中发挥作用。在本文中，我们回顾了已被证明可控制光散射和透明度的α-晶状体蛋白的物理化学性质和四级结构特征。讨论了晶状体蛋白混合物对晶状体功能的重要性。然后，提出了一种形式化方法来设计α-晶状体蛋白四级结构的模型，包括α-晶状体蛋白是否以对称方式组装的问题。与α-晶状体蛋白C末端结构域折叠相关的一个假说在本期的另一篇论文中提出。
