Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Bundoora, VIC 3086, Australia.
Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Bundoora, VIC 3086, Australia; Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Parkville, VIC 3010, Australia.
Structure. 2016 Aug 2;24(8):1282-1291. doi: 10.1016/j.str.2016.05.019. Epub 2016 Jul 14.
Dihydrodipicolinate synthase (DHDPS) catalyzes the first committed step in the lysine biosynthesis pathway of bacteria. The pathway can be regulated by feedback inhibition of DHDPS through the allosteric binding of the end product, lysine. The current dogma states that DHDPS from Gram-negative bacteria are inhibited by lysine but orthologs from Gram-positive species are not. The 1.65-Å resolution structure of the Gram-negative Legionella pneumophila DHDPS and the 1.88-Å resolution structure of the Gram-positive Streptococcus pneumoniae DHDPS bound to lysine, together with comprehensive functional analyses, show that this dogma is incorrect. We subsequently employed our crystallographic data with bioinformatics, mutagenesis, enzyme kinetics, and microscale thermophoresis to reveal that lysine-mediated inhibition is not defined by Gram staining, but by the presence of a His or Glu at position 56 (Escherichia coli numbering). This study has unveiled the molecular determinants defining lysine-mediated allosteric inhibition of bacterial DHDPS.
二氢二吡啶羧酸合酶（DHDPS）催化细菌赖氨酸生物合成途径中的第一步。该途径可以通过终产物赖氨酸的变构结合来反馈抑制 DHDPS 进行调节。目前的定论是，革兰氏阴性菌的 DHDPS 受到赖氨酸的抑制，但革兰氏阳性菌的同源物不受抑制。革兰氏阴性军团菌 DHDPS 的 1.65Å 分辨率结构和革兰氏阳性肺炎链球菌 DHDPS 的 1.88Å 分辨率结构与赖氨酸结合，以及全面的功能分析表明，这种定论是不正确的。随后，我们利用晶体学数据结合生物信息学、突变、酶动力学和微量热泳动技术，揭示了赖氨酸介导的抑制作用不是由革兰氏染色定义的，而是由位置 56（大肠杆菌编号）存在组氨酸或谷氨酸决定的。这项研究揭示了定义细菌 DHDPS 中赖氨酸介导的变构抑制的分子决定因素。
