Caulfield M P, Furlong D, Tai P C, Davis B D
Proc Natl Acad Sci U S A. 1985 Jun;82(12):4031-5. doi: 10.1073/pnas.82.12.4031.
The S complex of Bacillus subtilis, a set of four proteins that appears to be involved in protein secretion, is shown to be attached to 70S ribosomes: antibody to its 64-kDa component can aggregate these ribosomes, and the complex can be chemically crosslinked to ribosomal proteins. Low Mg2+ or prolonged high-speed centrifugation in a sucrose gradient releases the S complex from the ribosomes, and it is recovered as an aggregate with an S value of 76. Electron microscopy shows that these aggregates have a regular structure, somewhat resembling clathrin cages, with a diameter of about 45 nm. If these aggregates are physiological, their function would differ significantly from that of the signal recognition particle of eukaryotes.
枯草芽孢杆菌的S复合物是一组似乎参与蛋白质分泌的四种蛋白质，已证明它附着于70S核糖体：针对其64 kDa组分的抗体可使这些核糖体聚集，并且该复合物可与核糖体蛋白进行化学交联。低镁离子浓度或在蔗糖梯度中长时间高速离心可使S复合物从核糖体上释放出来，并且它以S值为76的聚集体形式回收。电子显微镜显示这些聚集体具有规则的结构，有点类似于网格蛋白笼，直径约为45 nm。如果这些聚集体具有生理学意义，那么它们的功能将与真核生物的信号识别颗粒的功能有显著差异。
