ATP-induced FliI hexamerization facilitates bacterial flagellar protein export
ATP-induced FliI hexamerization facilitates bacterial flagellar protein export
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DOI：
10.1016/j.bbrc.2009.08.004
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发表时间：
2009-10-16
影响因子：
3.1
通讯作者：
Namba, Keiichi
中科院分区：
文献类型：
--
作者：
Kazetani, Ken-ichi;Minamino, Tohru;Namba, Keiichi
FliI ATP酶形成同源六聚体以充分发挥其ATP酶活性，促进细菌鞭毛蛋白输出。然而，FliI六聚化如何与蛋白质输出相关联仍然是未知的。在这里，我们分析了FliI及其催化突变体的成环能力。与ATP相比，不可水解的ATP类似物增加了FliI六聚化的可能性。相反，FliI（E221 Q）保持了对ATP的亲和力，但失去了ATP酶活性，即使在ATP存在下也能有效地形成六聚体。这些突变降低了对ATP的结合亲和力，显著消除了环的形成。这些结果表明，ATP结合诱导FliI六聚化，ADP和Pi的释放使环结构不稳定。FliI（E221 Q）促进鞭毛蛋白出口的FliH调节器的出口装置的情况下，虽然不是在野生型FliI水平，而其他没有。我们建议，FliI耦合ATP的结合和水解，其组装-拆卸周期，有效地启动鞭毛蛋白输出周期。(C)2009 Elsevier Inc. All rights reserved.
FliI ATPase forms a homo-hexamer to fully exert its ATPase activity, facilitating bacterial flagellar protein export. However, it remains unknown how FliI hexamerization is linked to protein export. Here, we analyzed the capability of ring formation by FliI and its catalytic mutant variants. Compared to ATP a non-hydrolysable ATP analog increased the probability of FliI hexamerization. In contrast, FliI(E221Q), which retained the affinity for ATP but has lost ATPase activity, efficiently formed the hexamer even in the presence of ATP. The mutations, which reduced the binding affinity for ATP, significantly abolished the ring formation. These results indicate that ATP-binding induces FliI hexamerization and that the release of ADP and Pi destabilizes the ring structure. FliI(E221Q) facilitated flagellar protein export in the absence of the FliH regulator of the export apparatus although not at the wild-type FliI level while the other did not. We propose that FliI couples ATP binding and hydrolysis to its assembly-disassembly cycle to efficiently initiate the flagellar protein export cycle. (C) 2009 Elsevier Inc. All rights reserved.