Grallert H, Rutkat K, Buchner J
Institut für Biophysik & Physikalische Biochemie, Universität Regensburg, 93040 Regensburg, Germany.
J Biol Chem. 1998 Dec 11;273(50):33305-10. doi: 10.1074/jbc.273.50.33305.
The prokaryotic molecular chaperone GroE is increasingly expressed under heat shock conditions. GroE protects cells by preventing the irreversible aggregation of thermally unfolding proteins. Here, the interaction of GroE with thermally unfolding citrate synthase (CS) was dissected into several steps that occur before irreversible aggregation, and the conformational states of the unfolding protein recognized by GroEL were determined. The kinetic analysis of CS unfolding revealed the formation of inactive dimeric and monomeric intermediates. GroEL binds both intermediates without affecting the unfolding pathway. Furthermore, the dimeric intermediates are not protected against dissociation in the presence of GroEL. Monomeric CS is stably associated with GroEL, thus preventing further irreversible unfolding steps and subsequent aggregation. During refolding, monomeric CS is encapsulated inside the cavity of GroEL. GroES complexes. Taken together our results suggest that for protection of cells against heat stress both the ability of GroEL to interact with a large variety of nonnative conformations of proteins and the active, GroES-dependent refolding of highly unfolded species are important.
原核分子伴侣GroE在热休克条件下表达量不断增加。GroE通过防止热变性蛋白发生不可逆聚集来保护细胞。在此，将GroE与热变性柠檬酸合酶（CS）的相互作用解析为不可逆聚集之前发生的几个步骤，并确定了被GroEL识别的变性蛋白的构象状态。CS变性的动力学分析揭示了无活性二聚体和单体中间体的形成。GroEL与这两种中间体结合，而不影响变性途径。此外，在GroEL存在的情况下，二聚体中间体不会受到解离的影响。单体CS与GroEL稳定结合，从而防止进一步的不可逆变性步骤和随后的聚集。在复性过程中，单体CS被包裹在GroEL的腔内。GroES复合物。综合我们的结果表明，为保护细胞免受热应激，GroEL与多种蛋白质非天然构象相互作用的能力以及高度变性物种依赖GroES的活性复性都很重要。
