Co-translocation of a periplasmic enzyme complex by a hitchhiker mechanism through the bacterial Tat pathway
Co-translocation of a periplasmic enzyme complex by a hitchhiker mechanism through the bacterial Tat pathway
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DOI：
10.1074/jbc.274.19.13223
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发表时间：
1999-05-07
影响因子：
4.8
通讯作者：
Wu, LF
中科院分区：
文献类型：
--
作者：
Rodrigue, A;Chanal, A;Wu, LF
细菌周质含镍氢化酶由含有双精氨酸信号序列的小亚基和缺乏输出信号的大亚基组成。为了了解大亚基是如何转运到周质中的，我们克隆了编码大肠杆菌氢化酶2的hyb操纵子，构建了一个缺失突变体，并研究了氢化酶2的转运机制。当小亚基（Hyb O）或大亚基（Hyb C）中的一个在另一个亚基缺失的情况下表达时，它们中的一个作为前体积累在细胞质中，因此，与大多数经典分泌蛋白相反，如果大亚基缺失，则小亚基本身的信号序列不足以用于膜靶向和易位。另一方面，小亚基不仅是大亚基的膜靶向所必需的，而且也是大亚基获得镍所必需的。最有趣的是，小亚基的信号序列决定大亚基是否遵循Sec或双精氨酸易位途径。总的来说，这些结果首次为细菌中自然发生的搭便车共易位机制提供了令人信服的证据。
Bacterial periplasmic nickel-containing hydrogenases are composed of a small subunit containing a twin-arginine signal sequence and a large subunit devoid of an export signal. To understand how the large subunit is translocated into the periplasm, we cloned the hyb operon encoding the hydrogenase 2 of Escherichia coli constructed a deletion mutant, and studied the mechanism of translocation of hydrogenase 2, The small subunit (HybO) or the large subunit (HybC) accumulated in the cytoplasm as a precursor when either of them was expressed in the absence of the other subunit, Therefore, contrary to most classical secretory proteins, the signal sequence of the small subunit itself is not sufficient for membrane targeting and translocation if the large subunit is missing. On the other hand, the small subunit was required not only for membrane targeting of the large subunit, but also for the acquisition of nickel by the large subunit, Most interestingly, the signal sequence of the small subunit determines whether the large subunit follows the Sec or the twin-arginine translocation pathway. Taken together, these results provide for the first time compelling evidence for a naturally occurring hitchhiker co-translocation mechanism in bacteria.