Department of Biological Sciences, 14 Science Drive 4, National University of Singapore, Singapore 117543, Republic of Singapore.
J Struct Biol. 2010 Mar;169(3):277-85. doi: 10.1016/j.jsb.2009.12.024. Epub 2010 Jan 4.
Polyamines are essential in all branches of life. Biosynthesis of spermidine, one of the most ubiquitous polyamines, is catalyzed by spermidine synthase (SpeE). Although the function of this enzyme from Escherichia coli has been thoroughly characterised, its structural details remain unknown. Here, we report the crystal structure of E. coli SpeE and study its interaction with the ligands by isothermal titration calorimetry and computational modelling. SpeE consists of two domains - a small N-terminal beta-strand domain, and a C-terminal catalytic domain that adopts a canonical methyltransferase (MTase) Rossmann fold. The protein forms a dimer in the crystal and in solution. Structural comparison of E. coli SpeE to its homologs reveals that it has a large and unique substrate-binding cleft that may account for its lower amine substrate specificity.
多胺是所有生命分支中必不可少的。精胺的生物合成，最普遍的多胺之一，由精胺合酶（SpeE）催化。尽管来自大肠杆菌的这种酶的功能已被彻底研究，但它的结构细节仍然未知。在这里，我们报告了大肠杆菌 SpeE 的晶体结构，并通过等温滴定量热法和计算建模研究了它与配体的相互作用。SpeE 由两个结构域组成 - 一个小的 N 端β-链结构域和一个 C 端催化结构域，其采用典型的甲基转移酶（MTase）Rossmann 折叠。该蛋白质在晶体中和溶液中形成二聚体。与同源物的结构比较表明，它具有一个大而独特的底物结合裂缝，这可能解释了它较低的胺底物特异性。
