Lin An-Ping, Hakala Kevin W, Weintraub Susan T, McAlister-Henn Lee
Department of Biochemistry, University of Texas Health Science Center, 7703 Floyd Curl Dr., San Antonio, TX 78229-3900, USA.
Arch Biochem Biophys. 2008 Jun 1;474(1):205-12. doi: 10.1016/j.abb.2008.03.005. Epub 2008 Mar 10.
Yeast mutants lacking mitochondrial NAD(+)-specific isocitrate dehydrogenase (idhDelta) or aconitase (aco1Delta) were found to share several growth phenotypes as well as patterns of specific protein expression that differed from the parental strain. These shared properties of idhDelta and aco1Delta strains were eliminated or moderated by co-disruption of the CIT1 gene encoding mitochondrial citrate synthase. Gas chromatography/mass spectrometry analyses indicated a particularly dramatic increase in cellular citrate levels in idhDelta and aco1Delta strains, whereas citrate levels were substantially lower in idhDeltacit1Delta and aco1Deltacit1Delta strains. Exogenous addition of citrate to parental strain cultures partially recapitulated effects of high endogenous levels of citrate in idhDelta and aco1Delta strains. Finally, effects of elevated cellular citrate in idhDelta and aco1Delta mutant strains were partially alleviated by addition of iron or by an increase in pH of the growth medium, suggesting that detrimental effects of citrate are due to elevated levels of the ionized form of this metabolite.
缺乏线粒体NAD⁺特异性异柠檬酸脱氢酶（idhDelta）或乌头酸酶（aco1Delta）的酵母突变体被发现具有几种共同的生长表型以及与亲本菌株不同的特定蛋白质表达模式。idhDelta和aco1Delta菌株的这些共同特性通过编码线粒体柠檬酸合酶的CIT1基因的共破坏而被消除或缓和。气相色谱/质谱分析表明，idhDelta和aco1Delta菌株中细胞柠檬酸水平特别显著增加，而idhDeltacit1Delta和aco1Deltacit1Delta菌株中的柠檬酸水平则显著降低。向亲本菌株培养物中添加外源柠檬酸部分重现了idhDelta和aco1Delta菌株中内源性柠檬酸水平高的影响。最后，通过添加铁或提高生长培养基的pH值，idhDelta和aco1Delta突变菌株中细胞柠檬酸升高的影响得到部分缓解，这表明柠檬酸的有害影响是由于这种代谢物离子化形式的水平升高。
