Wang H W, Sui S
Department of Biological Sciences and Biotechnology, Tsinghua University, Beijing, 100084, China.
J Struct Biol. 2001 Apr;134(1):46-55. doi: 10.1006/jsbi.2001.4364.
The problem of pentamer packing on a two-dimensional plane is of concern not only in physics and mathematics but also in biology. The packing styles of pentamers may either be related to or reflect the physiological or biochemical properties of biological macromolecules. C-reactive protein (CRP), one of the classical members of the petraxin family, was recently two-dimensionally (2D) crystallized by us on lipid monolayers by specific adsorption (Wang, H. W., and Sui, S. F., 1999, J. Struct. Biol. 127, 283-286). Another type of the protein's 2D crystal under the same conditions was obtained in the present work. The new 2D crystal was studied using electron microscopy of negatively stained specimens followed by image processing. A projection map at 2.2-nm resolution was obtained. The previous 2D crystal (PI) and the current 2D crystal (PII) show different pentamer-packing styles. Both of them are closely related to the fivefold symmetry of the molecule itself. The coexistence and the spatial contiguity of the two types of pentamer assembly were observed in a visual field. The fivefold symmetrical macromolecule can form a pentiling pattern on a two-dimensional plane, which has never been reported in biological system before. The possible mechanism of the two-dimensional assembly of pentameric CRP on lipid monolayers is discussed.
五聚体在二维平面上的堆积问题不仅在物理学和数学领域受到关注，在生物学领域也备受关注。五聚体的堆积方式可能与生物大分子的生理或生化特性相关，或者反映了这些特性。C反应蛋白（CRP）是petraxin家族的经典成员之一，最近我们通过特异性吸附在脂质单层上对其进行了二维（2D）结晶（Wang, H. W., and Sui, S. F., 1999, J. Struct. Biol. 127, 283 - 286）。在本研究中，在相同条件下获得了该蛋白的另一种二维晶体。使用负染标本的电子显微镜和图像处理技术对新的二维晶体进行了研究。获得了分辨率为2.2纳米的投影图。先前的二维晶体（PI）和当前的二维晶体（PII）呈现出不同的五聚体堆积方式。它们都与分子本身的五重对称性密切相关。在一个视野中观察到了两种五聚体组装形式的共存和空间连续性。这种具有五重对称性的大分子能够在二维平面上形成五聚镶嵌图案，这在生物系统中此前从未有过报道。本文还讨论了五聚体CRP在脂质单层上进行二维组装的可能机制。
