Abstract
Membrane cytochrome b5 reductase is a pleiotropic oxidoreductase that uses primarily soluble reduced nicotinamide adenine dinucleotide (NADH) as an electron donor to reduce multiple biological acceptors localized in cellular membranes. Some of the biological acceptors of the reductase and coupled redox proteins might eventually transfer electrons to oxygen to form reactive oxygen species. Additionally, an inefficient electron transfer to redox acceptors can lead to electron uncoupling and superoxide anion formation by the reductase. Many efforts have been made to characterize the involved catalytic domains in the electron transfer from the reduced flavoprotein to its electron acceptors, such as cytochrome b5, through a detailed description of the flavin and NADH-binding sites. This information might help to understand better the processes and modifications involved in reactive oxygen formation by the cytochrome b5 reductase. Nevertheless, more than half a century since this enzyme was first purified, the one-electron transfer process toward potential electron acceptors of the reductase is still only partially understood. New advances in computational analysis of protein structures allow predicting the intramolecular protein dynamics, identifying potential functional sites, or evaluating the effects of microenvironment changes in protein structure and dynamics. We applied this approach to characterize further the roles of amino acid domains within cytochrome b5 reductase structure, part of the catalytic domain, and several sensors and structural domains involved in the interactions with cytochrome b5 and other electron acceptors. The computational analysis results allowed us to rationalize some of the available spectroscopic data regarding ligand-induced conformational changes leading to an increase in the flavin adenine dinucleotide (FAD) solvent-exposed surface, which has been previously correlated with the formation of complexes with electron acceptors.
Highlights
Instituto de Investigaciones Biomédicas ‘Alberto Sols’ (CSIC-UAM), Arturo Duperier, 4, Department of Biochemistry, Faculty of Medicine, Universidad Autónoma de Madrid (UAM), Arzobispo Morcillo, 4, 28029 Madrid, Spain
In Saccharomyces cerevisiae, mitochondrial cytochrome b5 reductase (Cb5 R) sorts into different mitochondrial compartments, due to 40 amino acid residues at the N-terminal end of the membrane isoform cytochrome b5 (Cb5) R not conserved in other flavoenzymes
We have reported that Cb5 R/Cb5 can be a source of reactive oxygen species using the purified enzyme, biological membranes, and culture cells [28,31,33]
Summary
Cb5 R membrane isoforms have N-terminal domains that anchor the soluble domain into the microsomal membrane [10,11], and the MOM [13]. The biological function of Cb5 R in membranes is facilitated by the membrane isoform of cytochrome b5 (Cb5 ), which possesses a membrane-binding domain in the protein structure and a water-soluble domain that interacts with the cytosol. Cb5 R can produce reactive oxygen species (ROS) in the absence of electron acceptors [15,20], Cb5 can be regarded as an antioxidant protein that prevents excessive intracellular ROS production during drug detoxification [18]. This effect can be considered as derived from microsomal cytochromes P450 requirement of two electrons and two protons for the oxidation of substrates. This fosters the Cb5 stimulatory effect through a more efficient coupling of the system components
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
