School of Dentistry, University of California, Los Angeles, CA 90095, USA.
Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, CA 90095, USA.
Microbiology (Reading). 2012 Sep;158(Pt 9):2336-2343. doi: 10.1099/mic.0.060103-0. Epub 2012 Jul 12.
The Clp/HSP100 family of molecular chaperones is ubiquitous in both prokaryotes and eukaryotes. These proteins play important roles in refolding, disaggregating and degrading proteins damaged by stress. As a subclass of the Clp/HSP100 family, ClpB has been shown to be involved in various stress responses as well as other functions in bacteria. In the present study, we investigated the role of a predicted ClpB-encoding gene, MXAN5092, in the stress response during vegetative growth and development of Myxococcus xanthus. Transcriptional analysis confirmed induction of this clpB homologue under different stress conditions, and further phenotypic analysis revealed that an in-frame deletion mutant of MXAN5092 was more sensitive to various stress treatments than the wild-type strain during vegetative growth. Moreover, the absence of the MXAN5092 gene resulted in decreased heat tolerance of myxospores, indicating the involvement of this clpB homologue in the stress response during the development of myxospores. The M. xanthus recombinant ClpB (MXAN5092) protein also showed a general chaperone activity in vitro. Overall, our genetic and phenotypic analysis of the predicted ATP-dependent chaperone protein ClpB (MXAN5092) demonstrated that it functions as a chaperone protein and plays an important role in cellular stress tolerance during both vegetative growth and development of M. xanthus.
Clp/HSP100 家族的分子伴侣在原核生物和真核生物中普遍存在。这些蛋白质在蛋白质的重折叠、解聚和降解方面发挥着重要作用，这些蛋白质因应激而受损。作为 Clp/HSP100 家族的一个亚类，ClpB 已被证明参与了细菌中的各种应激反应以及其他功能。在本研究中，我们研究了预测的 ClpB 编码基因 MXAN5092 在粘细菌（Myxococcus xanthus）营养生长和发育过程中的应激反应中的作用。转录分析证实了该 clpB 同源物在不同应激条件下的诱导，进一步的表型分析表明，在营养生长过程中，MXAN5092 的无框缺失突变体比野生型菌株对各种应激处理更为敏感。此外，MXAN5092 基因的缺失导致了粘孢子耐热性的降低，表明该 clpB 同源物参与了粘孢子发育过程中的应激反应。粘细菌重组 ClpB（MXAN5092）蛋白在体外也表现出普遍的伴侣活性。总的来说，我们对预测的依赖于 ATP 的伴侣蛋白 ClpB（MXAN5092）的遗传和表型分析表明，它作为伴侣蛋白发挥作用，并在粘细菌的营养生长和发育过程中对细胞应激耐受性起着重要作用。
