Bovine Complex I Is a Complex of 45 Different Subunits

Abstract

Mammalian mitochondrial complex I is a multisubunit membrane-bound assembly with a molecular mass approaching 1 MDa. By comprehensive analyses of the bovine complex and its constituent subcomplexes, 45 different subunits have been characterized previously. The presence of a 46th subunit was suspected from the consistent detection of a molecular mass of 10,566 by electrospray ionization mass spectrometry of subunits fractionated by reverse-phase high pressure liquid chromatography. The component was found associated with both the intact complex and subcomplex I␤, which represents most of the membrane arm of the complex, and it could not be resolved chromatographically from subunit SGDH (the subunit of bovine complex I with the N-terminal sequence Ser-Gly-Asp-His). It has now been characterized by tandem mass spectrometry of intact protein ions and shown to be a C-terminal fragment of subunit SGDH arising from a specific peptide bond cleavage between Ile-55 and Pro-56 during the electrospray ionization process. Thus, the subunit composition of bovine complex I has been established. It is a complex of 45 different proteins plus non-covalently bound FMN and eight iron-sulfur clusters.

Iromycins from Streptomyces sp. and from synthesis: New inhibitors of the mitochondrial electron transport chain

“…As shown in Figure 1 iromycin A (7) inhibited NADH oxidation half-maximally (IC 50 ) at a concentration of 140 ng/mL (0.461 μM). The IC 50 value for piericidin A 1 (5) in the same test system was 2.1 ng/ml (0.0050 µM), which is comparable with the values given in the literature. 13 Metabolite 7 with its isopropyl group as end cap is 7-fold more potent than 9…”

“…1 MDa) consists of 45 subunits, seven of them are encoded by mitochondrial DNA. 5 For detailed insights in the function and dysfunction of complex I and the affiliated physiological effects, specific inhibitors are irreplaceable agents and valuable biochemical tools. This has led to the identification of a number of inhibitors and their use in binding studies, 6 which already have extensively contributed to the ongoing investigation of the properties of the enzyme and its as yet unsolved dynamic mode of action.…”

The mitochondrial respiratory chain of the secondary green alga Euglena gracilis shares many additional subunits with parasitic Trypanosomatidae

“…In contrast, in all eukaryotes investigated so far, including T. brucei (Acestor, Zikova et al 2011), the mammal Bos taurus (Carroll et al, 2006), the yeast Yarrowia lipolytica (Angerer et al, 2011), the green alga Chlamydomonas reinhardtii (Cardol et al, 2004) and the amoeba Acanthamoeba castellanii (Gawryluk et al, 2012), CI has a molecular mass of ~900-1000 kDa. In green plants, mammals and fungi, CI has however been found in association with dimeric CIII and/or CIV, leading to supercomplexes of >1.5 MDa (Cardol et al, 2008;Dudkina et al, 2005;Schagger and Pfeiffer, 2000).…”

Inactivation of genes coding for mitochondrial Nd7 and Nd9 complex I subunits in Chlamydomonas reinhardtii. Impact of complex I loss on respiration and energetic metabolism

“…This membrane-bound enzymatic assembly of approximately 1000 kDa is composed of 45 subunits in the mammal Bos taurus (Carroll et al, 2006), 42 in the fungus Yarrowia lipolytica (Angerer et al, 2011), 49 in the land plant Arabidopsis thaliana (Peters et al, 2013) and 42 in the green alga Chlamydomonas reinhardtii (Cardol et al, 2004). At least 40 subunits are conserved in all eukaryotic lineages (Cardol, 2011).…”