Zahn R, Buckle A M, Perrett S, Johnson C M, Corrales F J, Golbik R, Fersht A R
Cambridge Centre for Protein Engineering, Department of Chemistry, University of Cambridge, United Kingdom.
Proc Natl Acad Sci U S A. 1996 Dec 24;93(26):15024-9. doi: 10.1073/pnas.93.26.15024.
The chaperonin GroEL is a large complex composed of 14 identical 57-kDa subunits that requires ATP and GroES for some of its activities. We find that a monomeric polypeptide corresponding to residues 191 to 345 has the activity of the tetradecamer both in facilitating the refolding of rhodanese and cyclophilin A in the absence of ATP and in catalyzing the unfolding of native barnase. Its crystal structure, solved at 2.5 A resolution, shows a well-ordered domain with the same fold as in intact GroEL. We have thus isolated the active site of the complex allosteric molecular chaperone, which functions as a "minichaperone." This has mechanistic implications: the presence of a central cavity in the GroEL complex is not essential for those representative activities in vitro, and neither are the allosteric properties. The function of the allosteric behavior on the binding of GroES and ATP must be to regulate the affinity of the protein for its various substrates in vivo, where the cavity may also be required for special functions.
伴侣蛋白GroEL是一种大型复合物，由14个相同的57 kDa亚基组成，其某些活性需要ATP和GroES。我们发现，对应于191至345位残基的单体多肽在无ATP时促进硫氰酸酶和亲环蛋白A的重折叠以及催化天然核糖核酸酶的解折叠方面具有十四聚体的活性。其晶体结构在2.5埃分辨率下解析，显示出一个排列有序的结构域，其折叠方式与完整的GroEL相同。我们由此分离出了变构分子伴侣复合物的活性位点，它起着“微型伴侣蛋白”的作用。这具有机制上的意义：GroEL复合物中中央腔的存在对于体外这些代表性活性并非必不可少，变构特性也是如此。变构行为在GroES和ATP结合上的功能必定是在体内调节蛋白质对其各种底物的亲和力，在体内该腔可能对于特殊功能也是必需的。
