Succinate-cytochrome c reductase (SCR)

Succinate-cytochrome c reductase (SCR) is a functional segment of the mitochondrial electron transport chain in Eimeria species, representing the integrated activity of Complex II (succinate dehydrogenase) and Complex III (ubiquinol-cytochrome c oxidoreductase) [1.1.1, 1.2.1]. It plays a vital role in the parasite's energy metabolism by catalyzing the transfer of electrons from succinate to cytochrome c, a process coupled to the generation of a proton gradient necessary for ATP synthesis via oxidative phosphorylation [1.2.2]. In Eimeria spp., which are apicomplexan protozoa responsible for coccidiosis in poultry and livestock, SCR is a validated therapeutic target for several anticoccidial agents [1.1.3, 1.3.1]. The triazinetrione compound toltrazuril is known to inhibit SCR activity, thereby disrupting the parasite's energy production and halting its intracellular development during stages such as schizogony and gametogony [1.1.2, 1.1.5]. Other drugs, including atovaquone and certain quinolones like decoquinate, also interfere with this pathway by targeting the cytochrome bc1 component of the complex [1.2.1]. While the respiratory chain of Eimeria exhibits unique features compared to its vertebrate hosts, the rapid emergence of drug-resistant strains remains a significant challenge for the long-term efficacy of treatments targeting this enzyme system [1.3.1, 1.3.2].

Other names

Complex II-IIISuccinate-cytochrome c oxidoreductaseSuccinate dehydrogenase-cytochrome c reductaseSuccinate:ubiquinol-cytochrome c oxidoreductase

Inhibition of the mitochondrial electron transport chain by blocking electron transfer from succinate to cytochrome c, thereby disrupting ATP synthesis and parasite development.