Functional similarities and differences of an archaeal Hsp70(DnaK) stress protein compared with its homologue from the bacterium Escherichia coli.
Functional similarities and differences of an archaeal Hsp70(DnaK) stress protein compared with its homologue from the bacterium Escherichia coli.
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DOI：
10.1016/j.jmb.2003.12.053
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发表时间：
2004-02
影响因子：
5.6
通讯作者：
M. Żmijewski;A. Macario;B. Lipińska
中科院分区：
文献类型：
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作者：
M. Żmijewski;A. Macario;B. Lipińska
古细菌是原核生物，但它们的一些陪伴系统类似于真核生物。此外，并非所有古细菌都拥有应激蛋白 Hsp70(DnaK)，而细菌和真核生物则毫无例外地拥有该蛋白。此外，古细菌 DnaK 的一级结构更像细菌，而不是真核同源物。这里报道的工作解决了两个问题：古细菌 Hsp70 蛋白是否是伴侣蛋白，就像它在其他两个系统发育域中的同源物一样？如果是的话，陪伴机制是细菌型还是真核型？数据表明，古细菌 Methanosarcina mazei 的 DnaK 蛋白在体外作为萤光素酶复性中的伴侣有效发挥作用，并且需要 DnaJ 和另一种细菌型伴侣 GrpE 来发挥其功能。 M.mazei DnaK 伴侣活性通过与细菌共伴侣 DnaJ 相互作用而增强，但不通过真核同源物 HDJ-2 增强。细菌 GrpE 和 DnaJ 均刺激 M.mazei DnaK 的 ATP 酶活性。 M.mazei DnaK 依赖性体外陪伴途径与用于比较的大肠杆菌相似。然而，体内分析表明也存在显着差异。 M.mazei dnaJ 和 grpE 基因拯救了缺乏这些基因的大肠杆菌突变体，但大肠杆菌 dnaK 突变体没有得到 M.mazei dnaK 基因的补充。因此，虽然体外测试的数据证明了 M.mazei 和大肠杆菌 DnaK 蛋白之间的功能相似性，但体内结果表明，在细胞内，这两个物种的伴侣是不同的。
Archaea are prokaryotes but some of their chaperoning systems resemble those of eukaryotes. Also, not all archaea possess the stress protein Hsp70(DnaK), in contrast with bacteria and eukaryotes, which possess it without any known exception. Further, the primary structure of the archaeal DnaK resembles more the bacterial than the eukaryotic homologues. The work reported here addresses two questions: Is the archaeal Hsp70 protein a chaperone, like its homologues in the other two phylogenetic domains? And, if so, is the chaperoning mechanism of bacterial or eukaryotic type? The data have shown that the DnaK protein of the archaeon Methanosarcina mazei functions efficiently as a chaperone in luciferase renaturation in vitro, and that it requires DnaJ, and the other bacterial-type chaperone, GrpE, to perform its function. The M.mazei DnaK chaperone activity was enhanced by interaction with the bacterial co-chaperone DnaJ, but not by the eukaryotic homologue HDJ-2. Both the bacterial GrpE and DnaJ stimulated the ATPase activity of the M.mazei DnaK. The M.mazei DnaK-dependent chaperoning pathway in vitro is similar to that of the bacterium Escherichia coli used for comparison. However, in vivo analyses indicate that there are also significant differences. The M.mazei dnaJ and grpE genes rescued E.coli mutants lacking these genes, but E.coli dnaK mutants were not complemented by the M.mazei dnaK gene. Thus, while the data from in vitro tests demonstrate functional similarities between the M.mazei and E.coli DnaK proteins, in vivo results indicate that, intracellularly, the chaperones from the two species differ.