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Spotlights on Recent JACS Publications.

■ PINPOINTING THE SOURCE OF SUPEROXIDE A molecular machinethe bc1 protein complexhelps generate the fuel of life, ATP, but at the same time is suspected of producing a superoxide, a reactive and mobile radical that is toxic and may accelerate aging. The bc1 protein complex pumps protons across the mitochondrial membrane using a series of redox reactions, moving electrons from quinol substrates to downstream proteins. An intermediate radical is created at each step, offering multiple opportunities for stray reactions to make a superoxide. However, because of the experimental challenges in detecting oxygen species, researchers are not sure where or how the protein complex produces a superoxide. To identify superoxide’s origin, Peter Husen and Ilia Solov’yov perform molecular dynamics simulations, charting the interactions between oxygen and bc1 in a water lipid/ membrane system (DOI: 10.1021/jacs.6b04849). In the simulation, the researchers track oxygen as it diffuses into the protein, looking for conditions that could produce a superoxide: close proximity to an electron donor and a noticeable binding time at a reaction site. The simulation shows that oxygen intermingles at several reaction sites in the bc1 protein complex, but that one site, named Qo, is particularly accessible to oxygen. The site is a likely candidate for superoxide production, though future studies with quantum chemical calculations will be needed for confirmation. Erika Gebel Berg, Ph.D.