Frydman J, Erdjument-Bromage H, Tempst P, Hartl F U
Department of Biological Sciences, Stanford University, California 94305, USA.
Nat Struct Biol. 1999 Jul;6(7):697-705. doi: 10.1038/10754.
The 62 kDa protein firefly luciferase folds very rapidly upon translation on eukaryotic ribosomes. In contrast, the chaperone-mediated refolding of chemically denatured luciferase occurs with significantly slower kinetics. Here we investigate the structural basis for this difference in folding kinetics. We find that an N-terminal domain of luciferase (residues 1-190) folds co-translationally, followed by rapid formation of native protein upon release of the full-length polypeptide from the ribosome. In contrast sequential domain formation is not observed during in vitro refolding. Discrete unfolding steps, corresponding to domain unfolding, are however observed when the native protein is exposed to increasing concentrations of denaturant. Thus, the co-translational folding reaction bears more similarities to the unfolding reaction than to refolding from denaturant. We propose that co-translational domain formation avoids intramolecular misfolding and may be critical in the folding of multidomain proteins.
62 kDa的萤火虫荧光素酶在真核生物核糖体上翻译时折叠非常迅速。相比之下，化学变性的荧光素酶在伴侣蛋白介导下的重折叠动力学则明显较慢。在此，我们研究了这种折叠动力学差异的结构基础。我们发现荧光素酶的N端结构域（1 - 190位氨基酸残基）在共翻译过程中折叠，随后在全长多肽从核糖体释放后迅速形成天然蛋白。相比之下，在体外重折叠过程中未观察到结构域的顺序形成。然而，当天然蛋白暴露于浓度不断增加的变性剂中时，会观察到与结构域解折叠相对应的离散解折叠步骤。因此，共翻译折叠反应与解折叠反应的相似性高于与从变性剂中重折叠的相似性。我们提出，共翻译结构域形成可避免分子内错误折叠，并且可能在多结构域蛋白的折叠中起关键作用。
