Evolution and Function of the Populus SABATH Family Reveal That a Single Amino Acid Change Results in a Substrate Switch
Evolution and Function of the Populus SABATH Family Reveal That a Single Amino Acid Change Results in a Substrate Switch
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杨属 SABATH 家族的进化和功能揭示单个氨基酸变化导致底物转换
DOI：
10.1093/pcp/pcx198
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发表时间：
2018-02-01
影响因子：
4.9
通讯作者：
Yang, Hai-Ling
中科院分区：
文献类型：
--
作者：
Han, Xue-Min;Yang, Qi;Yang, Hai-Ling
酶家族底物特异性的进化机制仍然知之甚少。植物SABATH甲基转移酶催化各种低分子量代谢物的羧基的甲基化。对植物中SABATH家族功能多样性的研究可以揭示该酶家族底物特异性的进化。先前的研究从大叶杨基因组中鉴定了28个SABATH基因。本研究对杨树SABATH基因家族进行了重新注释，并对该基因家族进行了分子进化、基因表达和生化分析。28个SABATH基因在基因结构、对非生物胁迫的表达反应和编码蛋白的酶学性质上存在明显差异，可分为三类。杨I类SABATH蛋白将IAA转化为甲基-IAA，II类SABATH蛋白将苯甲酸（BA）和水杨酸（SA）转化为甲基-BA和甲基-SA，而III类SABATH蛋白将法呢酸（FA）转化为甲基-FA。对于杨树II类SABATH蛋白，正向和反向诱变研究均表明PtSABATH 4和PtSABATH 24之间的单个氨基酸转换导致底物转换。我们的研究结果为酶家族底物特异性的进化提供了新的见解。
Evolutionary mechanisms of substrate specificities of enzyme families remain poorly understood. Plant SABATH methyltransferases catalyze methylation of the carboxyl group of various low molecular weight metabolites. Investigation of the functional diversification of the SABATH family in plants could shed light on the evolution of substrate specificities in this enzyme family. Previous studies identified 28 SABATH genes from the Populus trichocarpa genome. In this study, we re-annotated the Populus SABATH gene family, and performed molecular evolution, gene expression and biochemical analyses of this large gene family. Twenty-eight Populus SABATH genes were divided into three classes with distinct divergences in their gene structure, expression responses to abiotic stressors and enzymatic properties of encoded proteins. Populus class I SABATH proteins converted IAA to methyl-IAA, class II SABATH proteins converted benzoic acid (BA) and salicylic acid (SA) to methyl-BA and methyl-SA, while class III SABATH proteins converted farnesoic acid (FA) to methyl-FA. For Populus class II SABATH proteins, both forward and reverse mutagenesis studies showed that a single amino acid switch between PtSABATH4 and PtSABATH24 resulted in substrate switch. Our findings provide new insights into the evolution of substrate specificities of enzyme families.