Cyanuric acid hydrolase: evolutionary innovation by structural concatenation
Cyanuric acid hydrolase: evolutionary innovation by structural concatenation
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DOI：
10.1111/mmi.12249
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发表时间：
2013-06-01
影响因子：
3.6
通讯作者：
Scott, Colin
中科院分区：
文献类型：
--
作者：
Peat, Thomas S.;Balotra, Sahil;Scott, Colin
氰尿酸水解酶AtzD是一个新发现的开环酰胺酶家族的创始成员。我们报告了这个家族的第一个X射线结构，这是一种新的折叠（称为三角铁折叠），可能是通过三聚体YjgF超家族的单体串联和金属结合位点的获得而进化的。AtzD与结合底物（氰尿酸）和抑制剂（磷酸盐，巴比妥酸和三聚氰胺）的结构，沿着诱变研究，允许活性位点的鉴定。AtzD单体、活性位点和底物都具有三重旋转对称性，以至于活性位点具有三个潜在的Ser-Lys催化二联体。一个单一的催化二联体（Ser 85-Lys 42）的假设，基于生化证据和晶体学数据。一个合理的催化机制，根据这些意见也提出。与相关的巴比妥酶，酒吧，同源性模型的比较，用于推断负责底物特异性的活性位点残基，并在数据库中的68 AtzD样酶的同源性进行了分析，在这种结构-功能关系。
The cyanuric acid hydrolase, AtzD, is the founding member of a newly identified family of ring-opening amidases. We report the first X-ray structure for this family, which is a novel fold (termed the Toblerone' fold) that likely evolved via the concatenation of monomers of the trimeric YjgF superfamily and the acquisition of a metal binding site. Structures of AtzD with bound substrate (cyanuric acid) and inhibitors (phosphate, barbituric acid and melamine), along with mutagenesis studies, allowed the identification of the active site. The AtzD monomer, active site and substrate all possess threefold rotational symmetry, to the extent that the active site possesses three potential Ser-Lys catalytic dyads. A single catalytic dyad (Ser85-Lys42) is hypothesized, based on biochemical evidence and crystallographic data. A plausible catalytic mechanism based on these observations is also presented. A comparison with a homology model of the related barbiturase, Bar, was used to infer the active-site residues responsible for substrate specificity, and the phylogeny of the 68 AtzD-like enzymes in the database were analysed in light of this structure-function relationship.