Chapter 5 Use of ruthenium photooxidation techniques to study electron transfer in the cytochrome bc1 complex

An electron transfer path connects subunits of a mycobacterial respiratory supercomplex

We report a 3.5-angstrom-resolution cryo-electron microscopy structure of a respiratory supercomplex isolated from Mycobacterium smegmatis. It comprises a complex III dimer flanked on either side by individual complex IV subunits. Complex III and IV associate so that electrons can be transferred from quinol in complex III to the oxygen reduction center in complex IV by way of a bridging cytochrome subunit. We observed a superoxide dismutase-like subunit at the periplasmic face, which may be responsible for detoxification of superoxide formed by complex III. The structure reveals features of an established drug target and provides a foundation for the development of treatments for human tuberculosis.

Roles of DMSO-type ruthenium complexes in disaggregation of prion neuropeptide PrP106–126

DMSO-type ruthenium complexes with aromatic ligands disaggregate the mature PrP106–126 fibrilsviametal coordination and hydrophobic interaction.

Optimising the synthesis, polymer membrane encapsulation and photoreduction performance of Ru(II)- and Ir(III)-bis(terpyridine) cytochrome c bioconjugates

Ruthenium(II) and iridium(III) bis(terpyridine) complexes were prepared with maleimide functionalities in order to site-specifically modify yeast iso-1 cytochrome c possessing a single cysteine residue available for modification (CYS102). Single X-ray crystal structures were solved for aniline and maleimide Ru(II) 3 and Ru(II) 4, respectively, providing detailed structural detail of the complexes. Light-activated bioconjugates prepared from Ru(II) 4 in the presence of tris(2-carboxyethyl)-phosphine (TCEP) significantly improved yields from 6% to 27%. Photoinduced electron transfer studies of Ru(II)-cyt c in bulk solution and polymer membrane encapsulated specimens were performed using EDTA as a sacrificial electron donor. It was found that membrane encapsulation of Ru(II)-cyt c in PS140-b-PAA48 resulted in a quantum efficiency of 1.1 ± 0.3 × 10(-3), which was a two-fold increase relative to the bulk. Moreover, Ir(III)-cyt c bioconjugates showed a quantum efficiency of 3.8 ± 1.9 × 10(-1), equivalent to a ∼640-fold increase relative to bulk Ru(II)-cyt c.

Recent advances in cytochrome bc(1): inter monomer electronic communication?

The ubihydroquinone: cytochrome c oxidoreductase, or cytochrome bc(1), is a central component of photosynthetic and respiratory energy transduction pathways in many organisms. It contributes to the generation of membrane potential and proton gradient used for cellular energy production (ATP). The three-dimensional structures of cytochrome bc(1) indicate that its two monomers are intertwined to form a symmetrical homodimer. This unusual architecture raises the issue of whether the monomers operate independently, or function cooperatively during the catalytic cycle of the enzyme. In this review, recent progresses achieved in our understanding of the mechanism of function of dimeric cytochrome bc(1) are presented. New genetic approaches producing heterodimeric enzymes, and emerging insights related to the inter monomer electron transfer between the heme b cofactors of cytochrome bc(1) are described.