Irazusta Verónica, Moreno-Cermeño Armando, Cabiscol Elisa, Ros Joaquim, Tamarit Jordi
Grup de Bioquímica de l'Estrés Oxidatiu, Departament de Ciències Mèdiques Bàsiques, Facultat de Medicina, Universitat de Lleida, 25008 Lleida, Spain.
Free Radic Biol Med. 2008 May 1;44(9):1712-23. doi: 10.1016/j.freeradbiomed.2008.01.014. Epub 2008 Jan 30.
Iron accumulation has been associated with several pathological conditions such as Friedreich ataxia. This human disorder is caused by decreased expression of frataxin. Iron-overload triggers oxidative stress, but the main targets of such stress are not known. In yeast cells lacking the frataxin ortholog YFH1, we have identified a set of 14 carbonylated proteins, which include mitochondrial ATP synthase, phosphoglycerate kinase, pyruvate kinase, and molecular chaperones. Interestingly, most of the target proteins are magnesium- and/or nucleotide-binding proteins. This key feature leads us to postulate that when iron accumulates, chelatable iron replaces magnesium at the corresponding metal-binding site, promoting selective damage to these proteins. Consistent with this hypothesis, in vitro experiments performed with pure pyruvate kinase and phosphoglycerate kinase showed that oxidation of these proteins can be prevented by magnesium and increased by the presence of ATP. Also, chelatable iron, which forms complexes with nucleotides, showed a sevenfold increase in Deltayfh1 cells. Moreover, lowering chelatable iron in Deltayfh1 cells by desferrioxamine prevented enzyme inactivation. As a general conclusion, we propose that magnesium bound to proteins is replaced by chelatable iron when this metal accumulates. This mechanism explains selective protein oxidation and provides clues for better understanding of iron-overloading pathologies.
铁蓄积与多种病理状况相关，如弗里德赖希共济失调。这种人类疾病是由铁调素表达降低引起的。铁过载引发氧化应激，但其主要靶点尚不清楚。在缺乏铁调素直系同源物YFH1的酵母细胞中，我们鉴定出一组14种羰基化蛋白，其中包括线粒体ATP合酶、磷酸甘油酸激酶、丙酮酸激酶和分子伴侣。有趣的是，大多数靶蛋白都是镁结合蛋白和/或核苷酸结合蛋白。这一关键特征使我们推测，当铁蓄积时，可螯合铁会在相应的金属结合位点取代镁，从而对这些蛋白造成选择性损伤。与这一假设一致，用纯化的丙酮酸激酶和磷酸甘油酸激酶进行的体外实验表明，镁可防止这些蛋白的氧化，而ATP的存在会使其氧化增加。此外，与核苷酸形成复合物的可螯合铁在Δyfh1细胞中增加了7倍。此外，用去铁胺降低Δyfh1细胞中的可螯合铁可防止酶失活。总的来说，我们提出当这种金属蓄积时，与蛋白结合的镁会被可螯合铁取代。这一机制解释了选择性蛋白氧化，并为更好地理解铁过载疾病提供了线索。
