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首页> 外文期刊>Journal of Molecular Biology >Crystal structure of a thermophilic GrpE protein: insight into thermosensing function for the DnaK chaperone system.
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Crystal structure of a thermophilic GrpE protein: insight into thermosensing function for the DnaK chaperone system.

机译：嗜热GrpE蛋白的晶体结构：深入了解DnaK伴侣系统的热敏功能。

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摘要

A homodimeric GrpE protein functions as a nucleotide exchange factor of the eubacterium DnaK molecular chaperone system. The co-chaperone GrpE accelerates ADP dissociation from, and promotes ATP binding to, DnaK, which cooperatively facilitates the DnaK chaperone cycle with another co-chaperone, DnaJ. GrpE characteristically undergoes two-step conformational changes in response to elevation of the environmental temperature. In the first transition at heat-shock temperatures, a fully reversible and functionally deficient structural alteration takes place in GrpE, and then the higher temperatures lead to the irreversible dissociation of the GrpE dimer into monomers as the second transition. GrpE is also thought to be a thermosensor of the DnaK system, since it is the only member of the DnaK system that changes its structure reversibly and loses its function at heat-shock temperatures of various organisms. We here report the crystal structure of GrpE from Thermus thermophilus HB8 (GrpE(Tth)) at 3.23 A resolution. The resolved structure is compared with that of GrpE from mesophilic Escherichia coli (GrpE(Eco)), revealing structural similarities, particularly in the DnaK interaction regions, and structural characteristics for the thermal stability of GrpE(Tth). In addition, the structure analysis raised the possibility that the polypeptide chain in the reported GrpE(Eco) structure was misinterpreted. Comparison of these two GrpE structures combined with the results of limited proteolysis experiments provides insight into the protein dynamics of GrpE(Tth) correlated with the shift of temperature, and also suggests that the localized and partial unfolding at the plausible DnaK interaction sites of GrpE(Tth) causes functional deficiency of nucleotide exchange factor in response to the heat shock.
机译：同源二聚体GrpE蛋白充当真细菌DnaK分子伴侣系统的核苷酸交换因子。协同伴侣GrpE加速了与DnaK的ADP分离，并促进了与DnaK的ATP结合，这与另一个协同伴侣DnaJ共同促进了DnaK伴侣的循环。 GrpE响应于环境温度升高，特征性地经历了两步构象变化。在热激温度下的第一个转变中，GrpE中发生了完全可逆的且功能上不足的结构改变，然后更高的温度导致GrpE二聚体不可逆地解离为单体，成为第二个转变。 GrpE还被认为是DnaK系统的热传感器，因为它是DnaK系统中唯一可逆地改变其结构并在各种生物的热激温度下丧失其功能的成员。我们在这里报告了3.23 A分辨率的嗜热栖热菌HB8的GrpE的晶体结构（GrpE（Tth））。将解析的结构与中温大肠杆菌（GrpE（Eco））的GrpE进行比较，发现结构相似，尤其是在DnaK相互作用区域，以及GrpE（Tth）的热稳定性的结构特征。此外，结构分析增加了报告的GrpE（Eco）结构中多肽链被误解的可能性。将这两种GrpE结构进行比较，并结合有限的蛋白水解实验结果，可以深入了解与温度变化相关的GrpE（Tth）蛋白质动力学，并且还表明了在GrpE可能的DnaK相互作用位点的局部和部分展开（ Tth）响应于热激引起核苷酸交换因子的功能缺陷。

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