School of Life Science and Biotechnology, Kyungpook National University, Daegu 702-701, Republic of Korea.
Int J Biol Macromol. 2010 Jun;46(5):512-6. doi: 10.1016/j.ijbiomac.2010.03.005. Epub 2010 Mar 20.
Lysine biosynthesis has been of interest in plant research, because lysine is the most limiting amino acid in crop protein production. Dihydrodipicolinate synthase (DHDPS) catalyzes the branch point reaction leading to meso-diaminopimelate (DAP) and (S)-lysine in lysine biosynthesis. In this report, we present the crystal structure of DHDPS from the marine bacterium Hahella chejuensis (HcDHDPS) at 1.5 A resolution. The four subunits of the asymmetric unit assemble to form a tetramer with an approximate 222 symmetry. At the active site of HcDHDPS, three residues Tyr132, Thr43 and Tyr106 are observed to constitute a catalytic triad and are located at similar positions of the corresponding residues of Escherichia coli DHDPS. The structural similarities in the overall fold and the active site environment between these two enzymes imply that HcDHDPS functions by a mechanism similar to E. coli DHDPS. However, unlike E. coli DHDPS, HcDHDPS has a unique extensive dimer-dimer interface that is mediated by not only strong hydrophobic interactions but also a hydrogen bond network.
赖氨酸生物合成一直是植物研究的热点，因为赖氨酸是作物蛋白质生产中最受限制的氨基酸。二氢二吡啶羧酸合酶（DHDPS）催化分支点反应，生成赖氨酸生物合成中的中-二氨基庚二酸（DAP）和（S）-赖氨酸。在本报告中，我们展示了来自海洋细菌海氏肠杆菌（HcDHDPS）的 DHDPS 的晶体结构，分辨率为 1.5Å。不对称单元的四个亚基组装形成一个具有大约 222 度对称的四聚体。在 HcDHDPS 的活性位点，观察到三个残基 Tyr132、Thr43 和 Tyr106 构成催化三联体，并且位于大肠杆菌 DHDPS 相应残基的相似位置。这两种酶在整体折叠和活性位点环境方面的结构相似性表明，HcDHDPS 的功能机制类似于大肠杆菌 DHDPS。然而，与大肠杆菌 DHDPS 不同，HcDHDPS 具有独特的广泛二聚体-二聚体界面，这种界面不仅由强疏水相互作用介导，还由氢键网络介导。
