Agashe Vishwas R, Guha Suranjana, Chang Hung-Chun, Genevaux Pierre, Hayer-Hartl Manajit, Stemp Markus, Georgopoulos Costa, Hartl F Ulrich, Barral José M
Department of Cellular Biochemistry, Max Planck Institute of Biochemistry, Am Klopferspitz 18, D-82152 Martinsried, Germany.
Cell. 2004 Apr 16;117(2):199-209. doi: 10.1016/s0092-8674(04)00299-5.
Trigger factor and DnaK protect nascent protein chains from misfolding and aggregation in the E. coli cytosol, but how these chaperones affect the mechanism of de novo protein folding is not yet understood. Upon expression under chaperone-depleted conditions, multidomain proteins such as bacterial beta-galactosidase (beta-gal) and eukaryotic luciferase fold by a rapid but inefficient default pathway, tightly coupled to translation. Trigger factor and DnaK improve the folding yield of these proteins but markedly delay the folding process both in vivo and in vitro. This effect requires the dynamic recruitment of additional trigger factor molecules to translating ribosomes. While beta-galactosidase uses this chaperone mechanism effectively, luciferase folding in E. coli remains inefficient. The efficient cotranslational domain folding of luciferase observed in the eukaryotic system is not compatible with the bacterial chaperone system. These findings suggest important differences in the coupling of translation and folding between bacterial and eukaryotic cells.
触发因子和DnaK可保护新生蛋白质链在大肠杆菌胞质溶胶中不发生错误折叠和聚集，但这些伴侣蛋白如何影响新生蛋白质折叠机制尚不清楚。在伴侣蛋白缺失的条件下表达时，多结构域蛋白如细菌β-半乳糖苷酶（β-gal）和真核荧光素酶会通过一条快速但低效的默认途径折叠，该途径与翻译紧密偶联。触发因子和DnaK可提高这些蛋白质的折叠产率，但在体内和体外均会显著延迟折叠过程。这种效应需要将额外的触发因子分子动态招募到正在翻译的核糖体上。虽然β-半乳糖苷酶能有效利用这种伴侣蛋白机制，但荧光素酶在大肠杆菌中的折叠效率仍然很低。在真核系统中观察到的荧光素酶高效共翻译结构域折叠与细菌伴侣蛋白系统不兼容。这些发现表明细菌和真核细胞在翻译与折叠的偶联方面存在重要差异。
