9月15日,，癌癥研究方面的著名期刊《癌癥研究》（Cancer Research）以封面文章的形式發(fā)表了中科院生物物理研究所劉志杰課題組在肝臟疾病相關(guān)蛋白質(zhì)結(jié)構(gòu)與功能研究方面的最新成果,。該論文的標(biāo)題為“通過N10取代的葉酸類似物抑制人源5,10-次甲基四氫葉酸合成酶的結(jié)構(gòu)基礎(chǔ)”。
據(jù)悉,，葉酸依賴型單碳代謝途徑與一些重要的生命活動(dòng)密切相關(guān),，如嘌呤、胸苷和氨基酸代謝等,，對(duì)細(xì)胞的增殖和分化有著重要的調(diào)控作用,。該代謝途徑中的許多催化酶是癌癥化療和其它代謝類疾病的重要靶標(biāo)，目前市場(chǎng)上已有多種以該代謝途徑中的催化酶為靶標(biāo)的藥物用于臨床,。人源5,10-次甲基四氫葉酸合成酶(Homo sapiens 5,10-methenyltetrahydrofolate synthetase 簡(jiǎn)稱hMTHFS,，酶學(xué)分類名：EC 6.3.3.2)位于單碳代謝途徑的起始點(diǎn)，對(duì)代謝途徑下游單碳代謝的調(diào)控非常重要,。針對(duì)癌癥引起的基因組甲基化異常,、DNA和RNA的完整性、DNA的修復(fù)能力等,，hMTHFS都是一個(gè)非常關(guān)鍵的調(diào)控位點(diǎn),。因此，hMTHFS也是一個(gè)極具潛力的藥物靶點(diǎn),。
由于長(zhǎng)期以來缺乏hMTHFS的三維結(jié)構(gòu),，人們對(duì)其催化和調(diào)控的分子機(jī)制缺乏深入的了解，以hMTHFS為靶標(biāo)的藥物研發(fā)也進(jìn)展緩慢,。劉志杰課題組的該項(xiàng)研究工作報(bào)道了該催化酶的四種不同的復(fù)合物模型,，其中包括hMTHFS-ATP-底物的反應(yīng)中間態(tài)和產(chǎn)物的結(jié)構(gòu)，首次向人們揭示了hMTHFS催化反應(yīng)活性位點(diǎn)的組成,、參與催化反應(yīng)的重要氨基酸以及催化反應(yīng)的詳細(xì)過程,。該項(xiàng)研究成果為后續(xù)的基于結(jié)構(gòu)的藥物設(shè)計(jì)提供了寶貴的結(jié)構(gòu)信息，為癌癥化療和代謝疾病治療的新藥研制奠定了基礎(chǔ),。
該項(xiàng)工作主要由博士后武棟完成,，張榮光研究員亦參與了部分研究工作,。該研究課題得到了國(guó)家自然科學(xué)基金委、科技部,、衛(wèi)生部和中國(guó)科學(xué)院的資助。（生物谷Bioon.com）
生物谷推薦原始出處：
Cancer Research 69, 7294, September 15, 2009.
Structural Basis for the Inhibition of Human 5,10-Methenyltetrahydrofolate Synthetase by N10-Substituted Folate Analogues
Dong Wu1, Yang Li1, Gaojie Song1, Chongyun Cheng1, Rongguang Zhang2, Andrzej Joachimiak2, Neil Shaw1 and Zhi-Jie Liu1
1 National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China and 2 Structural Biology Center, Argonne National Laboratory, Argonne, Illinois
5,10-Methenyltetrahydrofolate synthetase (MTHFS) regulates the flow of carbon through the one-carbon metabolic network, which supplies essential components for the growth and proliferation of cells. Inhibition of MTHFS in human MCF-7 breast cancer cells has been shown to arrest the growth of cells. Absence of the three-dimensional structure of human MTHFS (hMTHFS) has hampered the rational design and optimization of drug candidates. Here, we report the structures of native hMTHFS, a binary complex of hMTHFS with ADP, hMTHFS bound with the N5-iminium phosphate reaction intermediate, and an enzyme-product complex of hMTHFS. The N5-iminium phosphate captured for the first time in our crystal structure unravels a unique strategy used by hMTHFS for recognition of the substrate and provides structural basis for the regulation of enzyme activity. Binding of N10-substituted folate analogues places Y152 in the middle of the channel connecting ATP binding site with the substrate binding pocket, precluding the positioning of -phosphate for a nucleophilic attack. Using the structures of hMTHFS as a guide, we have probed the role of residues surrounding the active site in catalysis by mutagenesis. The ensemble of hMTHFS structures and the mutagenesis data yield a coherent picture of the MTHFS active site, determinants of substrate specificity, and new insights into the mechanism of inhibition of hMTHFS.
