Cytochrome b (mitochondrial) (CYTB) (CYTB)

Fungal mitochondrial cytochrome b is a key transmembrane subunit of the cytochrome bc1 complex (Complex III), which is essential for the mitochondrial electron transport chain. It functions by mediating the transfer of electrons from ubiquinol to cytochrome c through the Q-cycle mechanism, contributing to the generation of a proton gradient across the inner mitochondrial membrane for ATP production [1][2]. The quinol outer (Qo) site of cytochrome b is a highly conserved pocket that serves as a major target for various agricultural fungicides, such as strobilurins (e.g., azoxystrobin), and clinical antiprotozoals like atovaquone [3][4]. These inhibitors bind to the Qo site, effectively blocking electron transfer and leading to energy depletion and oxidative stress within the fungal or parasitic cell [5]. However, the therapeutic utility of targeting this site is often challenged by the emergence of resistance, primarily driven by single nucleotide polymorphisms in the mitochondrial cob gene, such as the G143A mutation [6]. Understanding the structural biology of the Qo site is crucial for developing next-generation inhibitors that can overcome existing resistance mechanisms while maintaining selectivity over the host's mitochondrial complex [7].

Other names

Mitochondrial cytochrome bComplex III subunit cytochrome bUbiquinol-cytochrome c reductase subunit bQo site of cytochrome bc1 complexQuinol outer site of cytochrome b

Inhibition of the mitochondrial electron transport chain by binding to the quinol outer (Qo) site of the cytochrome bc1 complex, thereby blocking the oxidation of ubiquinol and preventing the generation of the proton motive force required for ATP synthesis.