FOLDING OF RIBONUCLEASE-A FROM A PARTIALLY DISORDERED CONFORMATION - KINETIC-STUDY UNDER TRANSITION CONDITIONS
FOLDING OF RIBONUCLEASE-A FROM A PARTIALLY DISORDERED CONFORMATION - KINETIC-STUDY UNDER TRANSITION CONDITIONS
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DOI：
10.1021/bi00306a023
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发表时间：
1984-01-01
期刊：
影响因子：
2.9
通讯作者：
SCHERAGA, HA
中科院分区：
文献类型：
--
作者：
LYNN, RM;KONISHI, Y;SCHERAGA, HA
用3.5M LiClO 4（pH 3.0）变性的牛胰腺RNA酶A具有某种有序构象，如α-RNA酶A的高保留所示。螺旋状、结构紧凑。LiClO 4的这种效果通过观察到α-LiClO 4的α-分离的S-肽的螺旋在3.5 M LiClO 4（pH 3.0）存在下稳定，如通过圆二色性和NMR测量的。保留的α-通过与脲变性RNase A（不具有有序结构）的动力学折叠进行比较，研究了脲变性RNase A的螺旋结构和紧密结构对RNase A折叠动力学的影响。与先前在折叠条件下的研究相反，动力学折叠/展开实验在这里进行，在天然和LiClO 4变性的RNase A之间的过渡区，和天然和尿素变性的RNase A之间。将测量的弛豫时间外推至三相点，其中天然RNA酶A、LiClO 4变性的RNA酶A和脲变性的RNA酶A具有相同的热力学稳定性并且处于相同的浓度，以便比较在相同溶剂条件下这2种过程的速率。在这些条件下，折叠和解折叠途径进行了研究，同时没有任何积累的中间体。与尿素变性的RNase A相比，LiClO 4变性的RNase A没有观察到折叠的显著加速。这表明核糖核酸酶A中的所有有序结构在其对折叠途径的影响方面是不等同的;一些可能起重要作用，而一些可能不起作用。看起来α- RNA酶A的S-肽部分中的一个或多个β-螺旋建立紧密结构的弯曲是那些在RNA酶A折叠中不起重要作用的有序结构之一。
Bovine pancreatic RNase A, denatured by 3.5 M LiClO4 (pH 3.0), has some ordered conformation as indicated by a high retention of .alpha.-helix and compact structure. This effect of LiClO4 was confirmed by the observation that the .alpha.-helix of isolated S-peptide is stabilized in the presence of 3.5 M LiClO4 (pH 3.0), as measured by circular dichroism and NMR. The effect of the retained .alpha.-helices and compact structure on the folding kinetics of RNase A was studied by comparison with the kinetic folding from urea-denatured RNase A, which has no ordered structure. In contrast to a previous study under folding conditions, the kinetic folding/unfolding experiments were carried out here in the transition regions between native and LiClO4-denatured RNase A, and between native and urea-denatured RNase A. The measured relaxation times were extrapolated to the triple point, where native RNase A, LiClO4-denatured RNase A, and urea-denatured RNase A have the same thermodynamic staiblity and are at the same concentration in order to compare the rates of these 2 processes under the same solvent conditions. Under these conditions, both folding and unfolding pathways are studied simultaneously without any accumulated intermediates. No significant acceleration of folding was observed from LiClO4-denatured RNase A as compared to that from urea-denatured RNase A. This indicates that all ordered structures in RNase A are not equivalent in their influence on the folding pathway; some may play an essential role and some may not. It appears that the .alpha.-helix in the S-peptide portion of RNase A and one or more .beta.-bends, which establish the compact structure, are among those ordered structures that do not play an essential role in the folding of RNase A.