Sekiya K, Satoh R, Danbara H, Futaesaku Y
Department of Microbiology, School of Pharmaceutical Sciences, Kitasato University, Tokyo, Japan.
J Bacteriol. 1993 Sep;175(18):5953-61. doi: 10.1128/jb.175.18.5953-5961.1993.
Streptolysin O (SLO) is a membrane-damaging toxin produced by most strains of group A beta-hemolytic streptococci. We performed ultrastructural analysis of SLO-derived lesions on erythrocyte membranes by examining electron micrographs of negatively stained preparations. SLO formed numerous arc- and ring-shaped structures with or without holes on membranes. Rings formed on intact cell membranes had an inner diameter of ca. 24 nm and had distinct borders of ca. 4.9 nm in width, but the diameter of rings varied from 24 to 30 nm on membranes of erythrocyte ghosts. Image analysis of electron micrographs demonstrated that each ring was composed of an inner and an outer layer. Each layer contained an array of 22 to 24 SLO molecules. On the top of the ring, we found a characteristic crown that projected from the cell membrane. The crown was separated by an electron-dense layer from the basal part of the ring that was embedded in the lipid bilayer of the erythrocyte membrane. Heights of the three parts, namely, the crown (head), the space (neck), and the basal portion (base), were ca. 3.2, 1.6, and 5.0 nm, respectively, and we postulated that these parts are the constituents of a single SLO molecule. The volumes of SLO molecules in the inner and outer layers were calculated to be 77 and 88 nm3. On the basis of a model of the structure of SLO, we propose some new details of the mechanisms of hemolysis by SLO toxin.
链球菌溶血素O（SLO）是大多数A组β溶血性链球菌菌株产生的一种膜损伤毒素。我们通过检查负染制剂的电子显微照片，对红细胞膜上SLO引起的损伤进行了超微结构分析。SLO在膜上形成了许多有孔或无孔的弧形和环形结构。完整细胞膜上形成的环内径约为24nm，边界宽度约为4.9nm，但在红细胞血影膜上，环的直径在24至30nm之间变化。电子显微照片的图像分析表明，每个环由内层和外层组成。每层包含22至24个SLO分子的阵列。在环的顶部，我们发现了一个从细胞膜突出的特征性冠。冠与嵌入红细胞膜脂质双层的环基部之间由一个电子致密层隔开。冠（头部）、间隙（颈部）和基部这三个部分的高度分别约为3.2、1.6和5.0nm，我们推测这些部分是单个SLO分子的组成部分。内层和外层中SLO分子的体积经计算分别为77和88nm³。基于SLO的结构模型，我们提出了SLO毒素溶血机制的一些新细节。
