Regulation of S-adenosylmethionine levels in Saccharomyces cerevisiae
Regulation of S-adenosylmethionine levels in Saccharomyces cerevisiae
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DOI：
10.1074/jbc.m308696200
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发表时间：
2003-10-31
影响因子：
4.8
通讯作者：
Appling, DR
中科院分区：
文献类型：
--
作者：
Chan, SY;Appling, DR
亚甲基四氢叶酸还原酶 (MTHFR) 催化 5,10-亚甲基四氢叶酸还原为 5-甲基四氢叶酸，用于在蛋氨酸生物合成中甲基化同型半胱氨酸。甲硫氨酸可被 ATP 激活，产生通用甲基供体 S-腺苷甲硫氨酸 (AdoMet)。此前，构建了由酵母 Met13p N 端催化结构域和拟南芥 MTHFR (AtMTHFR-1) C 端调节结构域组成的嵌合 MTHFR (Chimera-1)（Roje, S.、Chan, S. Y.、Kaplan, F.、Raymond, R. K.、Horne, D. W.、Appling, D. R. 和 Hanson, A. D. (2002)化学杂志，277，4056-4061）。表达 Chimera-1 的工程酵母 (SCY4) 积累的 AdoMet 含量是野生型的 100 倍以上，蛋氨酸含量是野生型的 7 倍以上。令人惊讶的是，SCY4没有表现出明显的生长缺陷。通过研究 AdoMet 的细胞内区室以及超积累模式，研究了酵母超积累 AdoMet 的能力。先前的研究已确定 AdoMet 分布在细胞质和液泡之间。表达 Chimera-1 且缺乏液泡（vps33 突变体）或液泡多磷酸盐（vtc1 突变体）的菌株在有利于 AdoMet 超积累的条件下生长时无法存活。当这些细胞在含有甘氨酸和甲酸盐的培养基中生长时，AdoMet 的超积累是一种强烈的现象，但当这些补充剂被丝氨酸替代时，AdoMet 的超积累现象不会发生。讨论了与同型半胱氨酸生物合成和硫代谢相关的营养依赖性 AdoMet 超积累效应的基础。
Methylenetetrahydrofolate reductase (MTHFR) catalyzes the reduction of 5,10-methylenetetrahydrofolate to 5-methyltetrahydrofolate, used to methylate homocysteine in methionine biosynthesis. Methionine can be activated by ATP to give rise to the universal methyl donor, S-adenosylmethionine (AdoMet). Previously, a chimeric MTHFR (Chimera-1) comprised of the yeast Met13p N-terminal catalytic domain and the Arabidopsis thaliana MTHFR (AtMTHFR-1) C-terminal regulatory domain was constructed (Roje, S., Chan, S. Y., Kaplan, F., Raymond, R. K., Horne, D. W., Appling, D. R., and Hanson, A. D. (2002) J. Biol. Chem. 277, 4056-4061). Engineered yeast (SCY4) expressing Chimera-1 accumulated more than 100-fold more AdoMet and 7-fold more methionine than the wild type. Surprisingly, SCY4 showed no appreciable growth defect. The ability of yeast to hyperaccumulate AdoMet was investigated by studying the intracellular compartmentation of AdoMet as well as the mode of hyperaccumulation. Previous studies have established that AdoMet is distributed between the cytosol and the vacuole. A strain expressing Chimera-1 and lacking either vacuoles (vps33 mutant) or vacuolar polyphosphate (vtc1 mutant) was not viable when grown under conditions that favored AdoMet hyperaccumulation. The hyperaccumulation of AdoMet was a robust phenomenon when these cells were grown in medium containing glycine and formate but did not occur when these supplements were replaced by serine. The basis of the nutrient-dependent AdoMet hyperaccumulation effect is discussed in relation to homocysteine biosynthesis and sulfur metabolism.