Landry S J, Gierasch L M
Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas 75235-9041.
Biochemistry. 1991 Jul 30;30(30):7359-62. doi: 10.1021/bi00244a001.
Chaperones facilitate folding and assembly of nascent polypeptides in vivo and prevent aggregation in refolding assays in vitro. A given chaperone acts on a number of different proteins. Thus, chaperones must recognize features present in incompletely folded polypeptide chains and not strictly dependent on primary structural information. We have used transferred nuclear Overhauser effects to demonstrate that the Escherichia coli chaperonin GroEL binds to a peptide corresponding to the N-terminal alpha-helix in rhodanese, a mitochondrial protein whose in vitro refolding is facilitated by addition of GroEL, GroES, and ATP. Furthermore, the peptide, which is unstructured when free in aqueous solution, adopts an alpha-helical conformation upon binding to GroEL. Modification of the peptide to reduce its intrinsic propensity to take up alpha-helical structure lowered its affinity for GroEL, but, nonetheless, it could be bound and took up a helical conformation when bound. We propose that GroEL interacts with sequences in an incompletely folded chain that have the potential to adopt an amphipathic alpha-helix and that the chaperonin binding site promotes formation of a helix.
伴侣蛋白在体内促进新生多肽的折叠与组装，并在体外复性实验中防止聚集。特定的伴侣蛋白作用于多种不同的蛋白质。因此，伴侣蛋白必须识别不完全折叠的多肽链中存在的特征，而不是严格依赖于一级结构信息。我们利用转移核Overhauser效应证明，大肠杆菌伴侣蛋白GroEL与对应于硫氰酸酶N端α-螺旋的肽段结合，硫氰酸酶是一种线粒体蛋白，其体外复性通过添加GroEL、GroES和ATP得以促进。此外，该肽段在水溶液中自由存在时无结构，但与GroEL结合后会形成α-螺旋构象。对该肽段进行修饰以降低其形成α-螺旋结构的内在倾向，会降低其对GroEL的亲和力，然而，它仍能被结合，并在结合时形成螺旋构象。我们提出，GroEL与不完全折叠链中具有形成两亲性α-螺旋潜力的序列相互作用，并且伴侣蛋白结合位点促进螺旋的形成。
