Holzmeister Christian, Gaupels Frank, Geerlof Arie, Sarioglu Hakan, Sattler Michael, Durner Jörg, Lindermayr Christian
Institute of Biochemical Plant Pathology, Helmholtz Zentrum München-German Research Center for Environmental Health, 85764 München/Neuherberg, Germany.
Institute of Structural Biology, Helmholtz Zentrum München-German Research Center for Environmental Health, 85764 München/Neuherberg, Germany.
J Exp Bot. 2015 Feb;66(3):989-99. doi: 10.1093/jxb/eru458. Epub 2014 Nov 26.
Despite the importance of superoxide dismutases (SODs) in the plant antioxidant defence system little is known about their regulation by post-translational modifications. Here, we investigated the in vitro effects of nitric oxide derivatives on the seven SOD isoforms of Arabidopsis thaliana. S-nitrosoglutathione, which causes S-nitrosylation of cysteine residues, did not influence SOD activities. By contrast, peroxynitrite inhibited the mitochondrial manganese SOD1 (MSD1), peroxisomal copper/zinc SOD3 (CSD3), and chloroplastic iron SOD3 (FSD3), but no other SODs. MSD1 was inhibited by up to 90% but CSD3 and FSD3 only by a maximum of 30%. Down-regulation of these SOD isoforms correlated with tyrosine (Tyr) nitration and both could be prevented by the peroxynitrite scavenger urate. Site-directed mutagenesis revealed that-amongst the 10 Tyr residues present in MSD1-Tyr63 was the main target responsible for nitration and inactivation of the enzyme. Tyr63 is located nearby the active centre at a distance of only 5.26 Å indicating that nitration could affect accessibility of the substrate binding pocket. The corresponding Tyr34 of human manganese SOD is also nitrated, suggesting that this might be an evolutionarily conserved mechanism for regulation of manganese SODs.
尽管超氧化物歧化酶（SOD）在植物抗氧化防御系统中很重要，但关于其通过翻译后修饰进行的调控却知之甚少。在此，我们研究了一氧化氮衍生物对拟南芥七种SOD同工型的体外影响。引起半胱氨酸残基S-亚硝基化的S-亚硝基谷胱甘肽对SOD活性没有影响。相比之下，过氧亚硝酸根抑制线粒体锰SOD1（MSD1）、过氧化物酶体铜/锌SOD3（CSD3）和叶绿体铁SOD3（FSD3），但不影响其他SOD。MSD1的活性被抑制高达90%，但CSD3和FSD3的活性最高仅被抑制30%。这些SOD同工型的下调与酪氨酸（Tyr）硝化相关，而过氧亚硝酸根清除剂尿酸可以防止两者发生。定点诱变显示，在MSD1中存在的10个Tyr残基中，Tyr63是导致该酶硝化和失活的主要靶点。Tyr63位于活性中心附近，距离仅为5.26 Å，这表明硝化可能会影响底物结合口袋的可及性。人类锰SOD相应的Tyr34也会被硝化，这表明这可能是一种进化上保守的调节锰SOD的机制。
