Zahn R, Spitzfaden C, Ottiger M, Wüthrich K, Plückthun A
Max-Planck-Institut für Biochemie, Protein Engineering Group, Martinsried, Germany.
Nature. 1994 Mar 17;368(6468):261-5. doi: 10.1038/368261a0.
Protein folding in vivo is mediated by helper proteins, the molecular chaperones, of which Hsp60 and its Escherichia coli variant GroEL are some of the best characterized. GroEL is an oligomeric protein with 14 subunits each of M(r) 60K, which possesses weak, co-operative ATPase activity and high plasticity. GroEL seems to interact with non-native proteins, binding one or two molecules per 14-mer in a 'central cavity', but little is known about the conformational state of the bound polypeptides. Here we use nuclear magnetic resonance techniques to show that the interaction of the small protein cyclophilin with GroEL is reversible by temperature changes, and all amide protons in GroEL-bound cyclophilin are exchanged with the solvent, although this exchange does not occur in free cyclophilin. The complete secondary structure of cyclophilin must be disrupted when bound to GroEL.
体内蛋白质折叠由辅助蛋白介导，即分子伴侣，其中热休克蛋白60（Hsp60）及其大肠杆菌变体GroEL是特征最明确的一些分子伴侣。GroEL是一种寡聚蛋白，有14个亚基，每个亚基的相对分子质量为60K，具有较弱的协同ATP酶活性和高可塑性。GroEL似乎与非天然蛋白质相互作用，在“中央腔”中每14聚体结合一两个分子，但对于结合多肽的构象状态了解甚少。在这里，我们使用核磁共振技术表明，小蛋白亲环蛋白与GroEL的相互作用可随温度变化而逆转，并且与GroEL结合的亲环蛋白中的所有酰胺质子都与溶剂发生交换，尽管这种交换在游离亲环蛋白中不会发生。当与GroEL结合时，亲环蛋白的完整二级结构必定会被破坏。
