ROLE OF DIFFUSION IN THE FOLDING OF THE ALPHA-SUBUNIT OF TRYPTOPHAN SYNTHASE FROM ESCHERICHIA-COLI
ROLE OF DIFFUSION IN THE FOLDING OF THE ALPHA-SUBUNIT OF TRYPTOPHAN SYNTHASE FROM ESCHERICHIA-COLI
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DOI：
10.1021/bi00460a027
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发表时间：
1990-02-27
期刊：
影响因子：
2.9
通讯作者：
MATTHEWS, CR
中科院分区：
文献类型：
--
作者：
CHRUNYK, BA;MATTHEWS, CR
α折叠过程中的限速步骤。色氨酸合成酶的亚基被认为是两个折叠单位的结合。为了探索扩散在这一限速步骤中的作用，研究了尿素诱导的蛋白质在一些粘度增强剂存在下的去折叠和重折叠。通过研究这些试剂对折叠单元解离、限速去折叠反应和复性限速步骤的反向的影响，简化了分析。在乙二醇组分存在下，随着助溶剂浓度的增加，松弛时间延长。当考虑到助溶剂对蛋白质稳定性的影响时，发现速率与溶液的粘度呈一元线性关系。甘油和低浓度葡萄糖也得到了类似的结果，表明这种影响是普遍的，并不是任何增粘剂所特有的。这些结果清楚地证明了α中限速折叠单元的缔合/解离反应。色氨酸合成酶的亚单位涉及一个扩散过程。
The rate-limiting step in the folding of the .alpha. subunit of tryptophan synthase has been proposed to be the association of two folding units. To probe the role of diffusion in this rate-limiting step, the urea-induced unfolding and refolding of the protein was examined in the presence of a number of viscosity-enhancing agents. The analysis was simplified by studying the effect of these agents on folding unit dissociation, the rate-limiting unfolding reaction, and the reverse of the rate-limiting step in refolding. In the presence of ethylene glycol, the relaxation times for unfolding to the same final conditions increased with increasing concentration of the cosolvent. When the effects of the cosolvent on protein stability were taken into account, the rates were found to show a unitary linear dependence on the viscosity of the solution. Similar results were obtained with glycerol and low concentrations of glucose, demonstrating that the effect is general and not specific to any viscogenic agent. These results clearly demonstrate that the rate-limiting folding unit association/dissociation reaction in the .alpha. subunit of tryptophan synthase involves a diffusional process.