Experimental evidence for the existence of a stable half-barrel subdomain in the (β/α)8-barrel fold
Experimental evidence for the existence of a stable half-barrel subdomain in the (β/α)8-barrel fold
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DOI：
10.1016/j.jmb.2008.07.040
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发表时间：
2008-10-03
影响因子：
5.6
通讯作者：
Yamagishi, Akihiko
中科院分区：
文献类型：
--
作者：
Akanuma, Satoshi;Yamagishi, Akihiko
（beta/alpha）（8）-桶是最常见的折叠酶之一。参与组氨酸生物合成的两种（β/α）（8）-桶酶的出现，其中每一种都具有双重对称结构，已经提出是串联复制和α（β/α）（4）-半桶融合的结果。然而，几乎没有证据表明在其他（β/α）（8）-桶蛋白的进化中存在祖先半桶。为了检测大肠杆菌N-（5 '-磷酸核糖基）邻氨基苯甲酸异构酶的（β/α）（8）-桶结构中祖先半桶的残余，我们设计了三个潜在的半桶单元（β/α）（1-4）、（β/α）（3-6）和（β/α）（5-8）。在这三种排列中，只有（β/α）（3-6）是稳定的;它存在于单体和二聚体形式之间的平衡中。因此，E.大肠杆菌可以作为半桶前体。（β/α）（3-6）的串联重复主要产生相当稳定的单体结构。这一结果表明，单共价组装的半桶的结构特性可以通过复制和融合来改善。此外，我们的研究结果可以提供有关的本地结构单元，包括这种无处不在的蛋白质构象的早期折叠事件的重要相互作用的信息。(C)2008爱思唯尔有限公司保留所有权利。
The (beta/alpha)(8)-barrel is one of the most common folds functioning as enzymes. The emergence of two (beta/alpha)(8)-barrel enzymes involved in histidine biossynthesis, each of which has a twofold symmetric structure, has been proposed to be a consequence of tandem duplication and fusion of a (beta/alpha)(4)-half-barrel. However, little evidence has been found for the existence of an ancestral half-barrel in the evolution of other (beta/alpha)(8)-barrel proteins. In order to detect remnants of an ancestral half-barrel in the (beta/alpha)(8)-barrel structure of Escherichia coli N-(5'-phosphoribosyl)anthranilate isomerase, we engineered three potential half-barrel units (beta/alpha)(1-4), (beta/alpha)(3-6), and (beta/alpha)(5-8). Among these three arrangements, only (beta/alpha)(3-6) is stable; it exists in equilibrium between monomeric and dimeric forms. Thus, the central segment of N-(5'-phosphoribosyl)anthranilate isomerase from E. coli can serve as a half-barrel precursor. A tandem duplication of (beta/alpha)(3-6) yielded predominantly monomeric structures that were quite stable. This result exemplified that the structural characteristics of moncovalently assembled half-barrels could be improved by duplication and fusion. Moreover, our results may provide information regarding the local structural units that encompass interactions important for the early folding events of this ubiquitous protein conformation. (C) 2008 Elsevier Ltd. All rights reserved.