The Arabidopsis AtPNG1 gene encodes a peptide:: N-glycanase
The Arabidopsis AtPNG1 gene encodes a peptide:: N-glycanase
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DOI：
10.1111/j.1365-313x.2007.03215.x
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发表时间：
2007-10-01
期刊：
影响因子：
7.2
通讯作者：
Brunner, Frederic
中科院分区：
文献类型：
--
作者：
Diepold, Andreas;Li, Guangtao;Brunner, Frederic
通过内质网相关降解（ERAD）途径的错误折叠蛋白质的去糖基化由在哺乳动物和酵母中高度保守的肽：N-聚糖酶（PNGases）催化。PNGases的催化机制采用由Cys、His和Asp残基组成的催化三联体，其由其他酶家族如半胱氨酸蛋白酶和蛋白质交联转氨酶（TGases）共享。与酵母和哺乳动物系统相反，对植物中的ERAD以及负责正确清除错误折叠的植物蛋白的酶知之甚少。我们已经使用了基于计算机的建模方法来确定拟南芥PNGase（AtPNG 1）。AtPNG 1由单拷贝基因编码，与已知的PNGases具有高度的结构同源性。重要的是，AtPNG 1的异源表达恢复了PNGase缺陷酿酒酵母突变体中的N-聚糖酶活性。AtPNG 1基因在植物的所有发育阶段均以低水平均匀地组成型表达，并且其表达似乎不受外部刺激的实质性调节。最近，报道了在大肠杆菌中产生的重组AtPNG 1显示TGase活性（Della Mea et al.，135，2046-54，2004）。然而，AtPNG 1基因的失活并没有导致突变体中TGase活性的降低，并且在S.酿酒酵母仅表现出残留的TGase活性。我们建议AtPNG 1基因编码一个真正的肽：N-聚糖酶，有助于ERAD相关的蛋白质在植物中的质量控制。
Deglycosylation of misfolded proteins by the endoplasmic reticulum-associated degradation (ERAD) pathway is catalyzed by peptide:N-glycanases (PNGases) that are highly conserved among mammals and yeast. The catalytic mechanism of PNGases employs a catalytic triad consisting of Cys, His and Asp residues, which is shared by other enzyme families such as cysteine proteases and protein cross-linking transglutaminases (TGases). In contrast to the yeast and mammalian systems, very little is known about ERAD in plants and the enzymes responsible for proper clearance of misfolded plant proteins. We have used a computer-based modeling approach to identify an Arabidopsis thaliana PNGase (AtPNG1). AtPNG1 is encoded by a single-copy gene and displays high structural homology with known PNGases. Importantly, heterologous expression of AtPNG1 restored N-glycanase activity in a PNGase-deficient Saccharomyces cerevisiae mutant. The AtPNG1 gene is uniformly and constitutively expressed at low levels throughout all developmental stages of the plant, and its expression does not appear to be subject to substantial regulation by external stimuli. Recently, recombinant AtPNG1 produced in Escherichia coli was reported to display TGase activity (Della Mea et al., Plant Physiol. 135, 2046-54, 2004). However, inactivation of the AtPNG1 gene did not result in decreased TGase activity in the mutant plant, and recombinant AtPNG1 produced in S. cerevisiae exhibited only residual TGase activity. We propose that the AtPNG1 gene encodes a bona fide peptide:N-glycanase that contributes to ERAD-related protein quality control in plants.