MACROMOLECULAR STRUCTURE

生物分子组装的结构和机制 主要研究了大分子和大分子络合物。 通过高分辨率电子显微镜和计算机图像 加工，但也包括其他信息，如氨基- 酸序列分析。在过去的一年里，我们取得了进展 主要在(1)冻结水化横向薄层分析中 松弛和僵硬的骨骼肌切片；(2)制定 纤维性受体识别蛋白的分子模型 呼肠孤病毒；以及(3)表征所发现的规则表面晶格 在两株百日咳杆菌的外膜中。 (1)对冷冻切片图像进行非线性对比度恢复后 转移纠正空间障碍，平均改善空间障碍 信噪比，我们观察到了信号的分布 在肌丝晶格的投影单胞内的质量 两个州都是。在进入僵硬状态时，质量从 肌球蛋白细丝的外围环绕肌动蛋白细丝。 我们还观察到影响肌球蛋白细丝僵硬的变化 在没有肌动蛋白的情况下。 (2)呼肠孤病毒粒子加热后释放的Sigma-1蛋白纤维 是同四聚体分子，长48 nm，宽5-9 nm。远端 杆子的一部分是由两根盘绕的螺旋绳索组成的 并肩而行。这部分之后是更大部分的约 与第一个相同的长度(23 Nm)，但更宽，包含 可见的亚结构，并富含β-折叠构象。 最后，羧基末端形成球状结构域，其中 受体结合位点驻留。 (3)应用广义图像平均技术，我们发现 百日咳杆菌表面格子是矩形的，观察到 P2对称性。它的单位细胞含有该细菌的两个三聚体 40K阴离子选择性孔蛋白，不同取向。这些都是 孔蛋白在晶体状态下是活跃的，这是正常的 表现出这种结构的菌株的生长速度。

The structures and mechanisms of assembly of biological macromolecules and macromolecular complexes are studied, primarily by high resolution electron microscopy and computer image processing, but also incorporating other information such as amino- acid sequence analyses. Over the past year, we have made headway primarily in (1) analysis of frozen-hydrated transverse thin sections of relaxed and rigor skeletal muscle; (2) formulating a molecular model for the fibrous receptor-recognition protein of reovirus; and (3) characterizing the regular surface lattice found in the outer membranes of two strains of Bordetella pertussis. (1) After restoring the cryo-section images for non-linear contrast transfer correcting for spatial disorders, and averaging to improve the signal-to-noise ratio, we have observed the distribution of mass within the projected unit cell of the myofilament lattice in both states. On entering rigor, mass is transferred from the periphery of the myosin filaments to surround the actin filaments. We also observe changes to affect myosin filaments in rigor even in the absence of actin. (2) Sigma-1 protein fibers released from reovirions upon heating are homotetrameric molecules, 48nm long x 5-9nm wide. The distal part of the rod is made up of two coiled-coil helical ropes placed side-by-side. This segment is followed by a wider portion of about the same length as the first (23nm) but which is wider, contains visible substructure, and is rich in beta-sheet conformation. Finally, the carboxy termini form globular domains where the receptor-combining sites reside. (3) Applying generalized image averaging techniques, we have found that the B. pertussis surface lattice is rectangular and observes p2 symmetry. Its unit cell contains two trimers of the bacterium's 40K anion-selective porin, in different orientations. That these porins are active in the crystalline state is implied by the normal growth rate of these strains that exhibit this structure.