Phillips G J, Silhavy T J
Department of Biology, College of William and Mary, Williamsburg, Virginia 23185.
Nature. 1992 Oct 22;359(6397):744-6. doi: 10.1038/359744a0.
Homologues of the gene encoding the 54K (M(r) 54,000) subunit of the mammalian signal recognition particle have been identified in different organisms. The Escherichia coli homologue, termed ffh (for fifty-four homologue), specifies a protein (Ffh) that shares many properties with its eukaryotic counterpart, including association with mammalian 7S RNA and the ability to bind signal sequences specifically. Ffh also associates with E. coli 4.5S RNA, showing that it can form a ribonucleoprotein complex in prokaryotes. These results are intriguing because extensive genetic and biochemical characterization of E. coli failed to identify a signal recognition particle-like mechanism for protein export. Here we address this issue directly by construction of a strain in which ffh expression is arabinose-dependent. Results of depletion experiments indicate that Ffh is important in protein translocation.
在不同生物体中已鉴定出编码哺乳动物信号识别颗粒54K（分子量54,000）亚基的基因的同源物。大肠杆菌的同源物称为ffh（五十四个同源物），它指定一种蛋白质（Ffh），该蛋白质与其真核对应物具有许多共同特性，包括与哺乳动物7S RNA结合以及特异性结合信号序列的能力。Ffh还与大肠杆菌4.5S RNA结合，表明它可以在原核生物中形成核糖核蛋白复合物。这些结果很有趣，因为对大肠杆菌进行的广泛遗传和生化表征未能鉴定出蛋白质输出的信号识别颗粒样机制。在这里，我们通过构建ffh表达依赖阿拉伯糖的菌株直接解决这个问题。缺失实验结果表明Ffh在蛋白质转运中很重要。
