Song Yingxian, Pu Hua, Jiang Tian, Zhang Lixin, Ouyang Min
Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, People's Republic of China.
Acta Crystallogr F Struct Biol Commun. 2016 Jun;72(Pt 6):448-56. doi: 10.1107/S2053230X16007263. Epub 2016 May 23.
Glutamate-1-semialdehyde-2,1-aminomutase (GSAM) catalyzes the isomerization of glutamate-1-semialdehyde (GSA) to 5-aminolevulinate (ALA) and is distributed in archaea, most bacteria and plants. Although structures of GSAM from archaea and bacteria have been resolved, a GSAM structure from a higher plant is not available, preventing further structure-function analysis. Here, the structure of GSAM from Arabidopsis thaliana (AtGSA1) obtained by X-ray crystallography is reported at 1.25 Å resolution. AtGSA1 forms an asymmetric dimer and displays asymmetry in cofactor binding as well as in the gating-loop orientation, which is consistent with previously reported Synechococcus GSAM structures. While one monomer binds PMP with the gating loop fixed in the open state, the other monomer binds either PMP or PLP and the gating loop is ready to close. The data also reveal the mobility of residues Gly163, Ser164 and Gly165, which are important for reorientation of the gating loop. Furthermore, the asymmetry of the AtGSA1 structure supports the previously proposed negative cooperativity between monomers of GSAM.
谷氨酸-1-半醛-2,1-氨基变位酶（GSAM）催化谷氨酸-1-半醛（GSA）异构化为5-氨基乙酰丙酸（ALA），分布于古菌、大多数细菌和植物中。尽管已解析了来自古菌和细菌的GSAM结构，但尚未获得高等植物的GSAM结构，这阻碍了进一步的结构-功能分析。在此，报道了通过X射线晶体学获得的拟南芥GSAM（AtGSA1）的结构，分辨率为1.25 Å。AtGSA1形成不对称二聚体，在辅因子结合以及门控环取向上表现出不对称性，这与先前报道的集胞藻GSAM结构一致。一个单体结合PMP时门控环固定在开放状态，而另一个单体结合PMP或PLP且门控环准备关闭。数据还揭示了对门控环重新定向很重要的Gly163、Ser164和Gly165残基的流动性。此外，AtGSA1结构的不对称性支持了先前提出的GSAM单体之间的负协同作用。
