Nature:細菌鞭毛分泌的動力來源並非ATP酶

生物谷報導：細菌鞭毛包含一個分泌器，它與很多病原體用來將效應器（effector）蛋白轉移進宿主細胞內的III-型分泌體系相關。科學家認為，ATP酶FliL為這種輸送提供能量，但本期Nature上兩篇論文反對這一被普遍接受的觀點。這兩個研究小組都發現，鞭毛分泌即使是在沒有這種ATP酶的情況下也能發生，而且為該過程提供能量的是質子運動力。

生物谷推薦英文原文：

Nature 451, 485-488 (24 January 2008) | doi:10.1038/nature06449; Received 8 August 2007; Accepted 29 October 2007

Distinct roles of the FliI ATPase and proton motive force in bacterial flagellar protein export

Tohru Minamino1,2 & Keiichi Namba1,2

1. Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka 565-0871, Japan
2. Dynamic NanoMachine Project, ICORP, JST, 1-3 Yamadaoka, Suita, Osaka 565-0871, Japan

Correspondence to: Keiichi Namba1,2 Correspondence and requests for materials should be addressed to K.N. (Email: [e-mail]).

Translocation of many soluble proteins across cell membranes occurs in an ATPase-driven manner. For construction of the bacterial flagellum responsible for motility, most of the components are exported by the flagellar protein export apparatus1, 2. The FliI ATPase is required for this export3, and its ATPase activity is regulated by FliH4; however, it is unclear how the chemical energy derived from ATP hydrolysis is used for the export process. Here we report that flagellar proteins of Salmonella enterica serovar Typhimurium are exported even in the absence of FliI. A fliH fliI double null mutant was weakly motile. Certain mutations in FlhA or FlhB, which form the core of the export gate, substantially improved protein export and motility of the double null mutant. Furthermore, proton motive force was essential for the export process. These results suggest that the FliH–FliI complex facilitates only the initial entry of export substrates into the gate, with the energy of ATP hydrolysis being used to disassemble and release the FliH–FliI complex from the protein about to be exported. The rest of the successive unfolding/translocation process of the substrates is driven by proton motive force.