截形苜蓿
拟南芥
生物
生物化学
拟南芥
生物合成
蛋白质亚单位
多胺
变构调节
蛋氨酸腺苷转移酶
ATP合酶
蛋氨酸
酶
突变体
氨基酸
遗传学
基因
共生
细菌
作者
B. Sekula,M. Ruszkowski,Zbigniew Dauter
标识
DOI:10.1016/j.ijbiomac.2020.02.100
摘要
S-adenosylmethionine synthases (MATs) are responsible for production of S-adenosylmethionine, the cofactor essential for various methylation reactions, production of polyamines and phytohormone ethylene, etc. Plants have two distinct MAT types (I and II). This work presents the structural analysis of MATs from Arabidopsis thaliana (AtMAT1 and AtMAT2, both type I) and Medicago truncatula (MtMAT3a, type II), which, unlike most MATs from other domains of life, are dimers where three-domain subunits are sandwiched flat with one another. Although MAT types are very similar, their subunits are differently oriented within the dimer. Structural snapshots along the enzymatic reaction reveal the exact conformation of precatalytic methionine in the active site and show a binding niche, characteristic only for plant MATs, that may serve as a lock of the gate loop. Nevertheless, plants, in contrary to mammals, lack the MAT regulatory subunit, and the regulation of plant MAT activity is still puzzling. Our structures open a possibility of an allosteric activity regulation of type I plant MATs by linear compounds, like polyamines, which would tighten the relationship between S-adenosylmethionine and polyamine biosynthesis.
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