2 0 0 0 高度好熱菌由来ホモセリン脱水素酵素の結晶学的研究
- 著者
- 赤井 翔太 生城 浩子 澤井 大樹 林 秀行 神谷 信夫 宮原 郁子
- 出版者
- 公益社団法人 日本ビタミン学会
- 雑誌
- ビタミン (ISSN:0006386X)
- 巻号頁・発行日
- vol.88, no.7, pp.358-365, 2014
Homoserine dehydrogenase catalyzes the conversion of L-aspartate-4-semialdehyde to L-homoserine. Homoserine dehydrogenase is required for the biosynthesis of the three essential amino acids, i.e. lysine, methionine, and isoleucine, from aspartic acid. This enzyme attracts attention also as a promising antifungal drug target. We have determined the crystal structures of homoserine dehydrogenase from Thermus thermophilus HB8 in both substrate-free form and homoserine-binding form by X-ray diffraction. Crystallization conditions were surveyed at 293 K by using a hanging-drop vapor-diffusion method. The substrate-free form was solved to 1.4 Å resolution and the homoserine-binding form was solved to 2.0 Å resolution. The homoserine dehydrogenase was a dimer with each subunit composed of three distinct domains, nucleotide-binding, dimerization, and substrate-binding domain. In the homoserine-binding forms, the amino group of homoserine made a hydrogen bond to the side chain carboxylate of Glu180. This hydrogen bond induced the conformation change of Thr165-Pro183 loop, which made the loop close to the active site. The substrate homoserine was rigidly recognized by several amino acid residues in the enzyme active site, indicating that Lys99 or Lys195 would be an essential catalytic residue to facilitate hydride transfer.
1 0 0 0 OA 放射光X線結晶構造解析による光合成・光化学系IIの水分解・酸素発生機構の解明
- 著者
- 神谷 信夫 沈 建仁
- 出版者
- 日本結晶学会
- 雑誌
- 日本結晶学会誌 (ISSN:03694585)
- 巻号頁・発行日
- vol.59, no.2-3, pp.64-71, 2017-06-30 (Released:2017-07-01)
- 参考文献数
- 45
- 被引用文献数
- 4
Photosystem II (PSII) is a multi-subunit protein complex embedded in the thylakoid membrane and splits water molecules, producing electrons, protons and molecular oxygen in photosynthesis. We started to purify and crystallize PSII in 1990, which led to the first crystal structure analysis at a resolution of 3.7 Å in 2003 using SPring-8. The resolution of the structure was raised to 1.9 Å in 2011, which was considered a breakthrough in the filed of photosynthesis because, on the basis of this atomic resolution structure, it became possible to discuss the molecular mechanism of the water-splitting reaction. We are continuing our studies to obtain much more precise information on the oxygen-evolving complex (OEC) at the S1-state of the Kok cycle and to analyze the intermediate state structures using femtosecond X-ray pulses from XFEL of SACLA.