Conformational stability and multistate unfolding of poly(A)-specific ribonuclease
Conformational stability and multistate unfolding of poly(A)-specific ribonuclease
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聚腺苷酸特异性核糖核酸酶的构象稳定性和多态解折叠
DOI：
10.1111/j.1742-4658.2009.07008.x
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发表时间：
2009-05-01
期刊：
影响因子：
5.4
通讯作者：
Yan, Yong-Bin
中科院分区：
文献类型：
--
作者：
He, Guang-Jun;Zhang, Ao;Yan, Yong-Bin
Poly(A) 特异性核糖核酸酶 (PARN) 以高度持续模式特异性催化单链 mRNA 的 Poly(A) 尾部的降解。 PARN 通过充当 mRNA 稳定性和翻译效率的调节剂来参与多种重要的细胞内过程。在本文中，使用盐酸胍和尿素作为化学变性剂研究了 PARN 的平衡解折叠。 PARN 的展开被表征为多态过程，但当被两种变性剂变性时涉及不同的平衡中间体。这些中间体光谱特征的比较表明，低浓度化学变性剂下的构象变化更可能是三级和四级结构的重排。特别是，一种无活性的熔球状中间体被鉴定为以可溶性非天然低聚物的形式存在，并且低聚物的形成通过静电相互作用来调节。尿素诱导的去折叠所特有的活性二聚体中间体的特征在于具有增加的规则二级结构和修饰的三级结构，这意味着环境压力可以诱导额外的规则结构。盐酸胍和尿素诱导的解折叠途径的差异表明静电相互作用在 PARN 稳定性和调节中发挥重要作用。多种具有不同性质的中间体的出现为PARN通过构象变化的多级调控提供了结构基础。
Poly(A)-specific ribonuclease (PARN) specifically catalyzes the degradation of the poly(A) tails of single-stranded mRNAs in a highly processive mode. PARN participates in diverse and important intracellular processes by acting as a regulator of mRNA stability and translational efficiency. In this article, the equilibrium unfolding of PARN was studied using both guanidine hydrochloride and urea as chemical denaturants. The unfolding of PARN was characterized as a multistate process, but involving dissimilar equilibrium intermediates when denatured by the two denaturants. A comparison of the spectral characteristics of these intermediates indicated that the conformational changes at low concentrations of the chemical denaturants were more likely to be rearrangements of the tertiary and quaternary structures. In particular, an inactive molten globule-like intermediate was identified to exist as soluble non-native oligomers, and the formation of the oligomers was modulated by electrostatic interactions. An active dimeric intermediate unique to urea-induced unfolding was characterized to have increased regular secondary structures and modified tertiary structures, implying that additional regular structures could be induced by environmental stresses. The dissimilarity in the unfolding pathways induced by guanidine hydrochloride and urea suggest that electrostatic interactions play an important role in PARN stability and regulation. The appearance of multiple intermediates with distinct properties provides the structural basis for the multilevel regulation of PARN by conformational changes.