Electron Transport Chain (Complex I, III, IV) Antibody Sampler Kit

Background

Mitochondrial acyl carrier protein (ACP) is an essential component in fatty acid biosynthesis in mitochondria. It is also known as NADH-ubiquinone oxidoreductase subunit AB1 (NDUFAB1), a Complex I subunit in the electron transport chain (ETC). NDUFAB1 regulates energy and reactive oxygen species (ROS) metabolism in mitochondria by coordinating the assembly of ETC Complexes I, II, and III, and supercomplexes (1). NDUFS1 (NADH dehydrogenase Fe-S protein 1) is a nuclear-encoded structural subunit of NADH: ubiquinone oxidoreductase (Complex I) in the mitochondrial ETC (2). Mutations in NDUFS1 and other Complex I subunits leading to mitochondrial dysfunction are associated with a number of neurological disorders (3-6). Ubiquinol-cytochrome c reductase iron-sulfur subunit (UQCRFS1), also known as Rieske iron-sulfur protein (RISP), is a component of Complex III in the mitochondrial ETC. UQCRFS1/RISP and two other subunits, cytochrome b (MT-CYB) and cytochrome c1 (CYC1), are essential for the catalytic activity of Complex III (7). Cytochrome c is a well conserved electron transport protein and is part of the respiratory chain localized to mitochondrial intermembrane space (8). Upon apoptotic stimulation, cytochrome c released from mitochondria associates with procaspase-9 (47 kDa)/Apaf-1. This complex processes caspase-9 from inactive proenzyme to its active form (9). This event further triggers caspase-3 activation and eventually leads to apoptosis (10). The mitochondrial ETC comprises multiple protein complexes, including cytochrome c oxidase. Cytochrome c oxidase catalyzes the reduction of oxygen to water. This process is coupled with pumping protons from the mitochondrial matrix into mitochondrial intermembrane space, contributing to the proton gradient used for ATP synthesis (11). Cytochrome c oxidase consists of 3 mitochondrial DNA-encoded subunits (COX1/MT-CO1, COX2/MT-CO2, and COX3/MT-CO3) and multiple nuclear DNA-encoded subunits (12). Research studies show that the mRNAs of the mitochondrially encoded oxidative phosphorylation subunits, including COX1/MT-CO1, decline significantly during aging (13). Cytochrome c oxidase (COX, also known as Complex IV) is a hetero-oligomeric enzyme consisting of 13 subunits localized to the inner mitochondrial membrane (14-16). It is the terminal enzyme complex in the respiratory chain, catalyzing the reduction of molecular oxygen to water coupled to the translocation of protons across the mitochondrial inner membrane to drive ATP synthesis. The 3 largest subunits forming the catalytic core are encoded by mitochondrial DNA, while the other smaller subunits, including COX IV, are nuclear-encoded. Research studies have shown that deficiency in COX activity correlates with a number of human diseases (17). COX10 is an assembly factor for cytochrome c oxidase in the mitochondrial ETC (18,19). Studies show that, when the gene encoding the β2-adrenergic receptor (Adrb2) is deleted, increased oxidative phosphorylation in endothelial cells inhibits angiogenesis. Deletion of Cox10 prevents the metabolic switch to oxidative phosphorylation in endothelial cells deleted of Adrb2, causing angiogenesis and cancer progression (19). In addition, COX10 contributes to T cell quiescence exit and is critical for T cell activation (20).