Abstract
Complex I (NADH dehydrogenase) is the first enzyme in the respiratory chain. It catalyses the electron transfer from NADH to ubiquinone that is associated with proton pumping out of the matrix. In this study, we characterized NADH dehydrogenase activity in seven monoxenous trypanosomatid species: Blechomonas ayalai, Herpetomonas tarakana, Kentomonas sorsogonicus, Leptomonas seymouri, Novymonas esmeraldas, Sergeia podlipaevi and Wallacemonas raviniae. We also investigated the subunit composition of the complex I in dixenous Phytomonas serpens, in which its presence and activity have been previously documented. In addition to P. serpens, the complex I is functionally active in N. esmeraldas and S. podlipaevi. We also identified 24-32 subunits of the complex I in individual species by using mass spectrometry. Among them, for the first time, we recognized several proteins of the mitochondrial DNA origin.
Highlights
NADH:ubiquinone oxidoreductase [EC 7.1.1.2], eukaryotic complex I, is the largest and the most complicated enzyme of the respiratory chain
We selected species from different clades of Trypanosomatidae (Lukeš et al, 2018). These are the members of the subfamilies Leishmaniinae (Kostygov and Yurchenko, 2017) (L. seymouri and N. esmeraldas), Strigomonadinae (Votýpka et al, 2014) (K. sorsogonicus), Phytomonadinae (Yurchenko et al, 2016) (H. tarakana), Blechomonadinae (Votýpka et al, 2013) (B. ayalai), as well as two genera not formally classified into any subfamily – Sergeia (Svobodová et al, 2007) and Wallacemonas (Kostygov et al, 2014)
Novymonas esmeraldas and K. sorsogonicus harbour endosymbiotic bacteria, which have been acquired by host species independently in evolution (Kostygov et al, 2017; Silva et al, 2018), while L. seymouri and B. ayalai are heavily infected with dsRNA viruses (Grybchuk et al, 2018a, 2018b)
Summary
NADH:ubiquinone oxidoreductase [EC 7.1.1.2], eukaryotic complex I, is the largest and the most complicated enzyme of the respiratory chain. The hydrophobic P-module (composed of the ND1, ND2, ND4 and ND5 multi-protein modules taking part in the proton pumping) is embedded in the inner mitochondrial membrane (Yagi and Matsuno-Yagi, 2003; Brandt, 2006, 2013; Berrisford and Sazanov, 2009). The core of this enzyme consists of 14 essential subunits that are fairly conserved across different domains of life (Gabaldón et al, 2005). Two of the most commonly used inhibitors of the mitochondrial complex I are rotenone (stabilizing the semiquinone intermediate within the complex) and capsaicin (antagonizing either formation or release of the quinol product) (Degli Esposti, 1998; Okun et al, 1999)
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