Nelson D R, Cumsky M G, Zusman D R
J Biol Chem. 1981 Dec 10;256(23):12589-95.
During the period of developmental aggregation which precedes fruiting body formation, the bacterium Myxococcus xanthus produces a large amount of a lectin called myxobacterial hemagglutinin (MBHA). Sequential cell washing, osmotic shock, and disruption of developmental cells showed that as much as 90% of the total hemagglutinating activity can be recovered in the wash and shock fractions. Analysis of the wash and shock fluids by sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that these fractions are enriched in MBHA. MBHA was detected on the surface of developmental cells but not vegetative cells by immunofluorescent staining procedures. The fluorescence was localized in distinct patches which were usually located at one or both of the cell poles, although patches of fluorescence could also be seen at additional sites as well. The presence of MBHA on the cell surface was also detected by electron microscopy of developmental cells stained with ferritin-conjugated antibody. Most of the cells showed distinct patches of ferritin staining at one or both of the cell poles; nonpolar staining, which was also observed, was always accompanied by membrane protuberances. The amino acid sequence of the NH2 terminus of MBHA was determined and found to be extremely hydrophobic, suggesting that it may function as a nonprocessed signal for transmembrane transport. The site-specific localization of MBHA at the cell poles suggests that it may function in end-to-end cellular interactions during aggregation.
在形成子实体之前的发育聚集期，黄色黏球菌会产生大量名为黏细菌血凝素（MBHA）的凝集素。对发育中的细胞进行连续的细胞洗涤、渗透休克处理以及细胞破碎后发现，高达90%的总血凝活性可在洗涤液和休克处理后的组分中回收。通过十二烷基硫酸钠-聚丙烯酰胺凝胶电泳对洗涤液和休克处理后的液体进行分析表明，这些组分富含MBHA。通过免疫荧光染色程序在发育中的细胞表面检测到了MBHA，但在营养细胞表面未检测到。荧光定位于不同的斑块中，这些斑块通常位于细胞的一极或两极，不过在其他位置也能看到荧光斑块。用铁蛋白偶联抗体对发育中的细胞进行电子显微镜观察也检测到了细胞表面存在MBHA。大多数细胞在细胞的一极或两极显示出明显的铁蛋白染色斑块；观察到的非极性染色总是伴随着膜突起。测定了MBHA氨基末端的氨基酸序列，发现其具有极强的疏水性，这表明它可能作为跨膜转运的未加工信号发挥作用。MBHA在细胞两极特异性定位表明它可能在聚集过程中的细胞端对端相互作用中发挥作用。
