Edited by Yifan Cheng, University of California, San Francisco, CA, and approved January 19, 2021 (received for review October 11, 2020)In the last steps of food oxidation in living organisms, electrons are transferred to oxygen through the membrane-bound respiratory chain. This electron transfer is mediated by mobile carriers, such as membrane-bound quinone and water-soluble cytochrome c. The latter transfers electrons from respiratory complex III to complex IV. In yeast, these complexes assemble into III2IV1/2 supercomplexes, but its role has remained enigmatic. This study establishes a...…Edited by Yifan Cheng, University of California, San Francisco, CA, and approved January 19, 2021 (received for review October 11, 2020)In the last steps of food oxidation in living organisms, electrons are transferred to oxygen through the membrane-bound respiratory chain. This electron transfer is mediated by mobile carriers, such as membrane-bound quinone and water-soluble cytochrome c. The latter transfers electrons from respiratory complex III to complex IV. In yeast, these complexes assemble into III2IV1/2 supercomplexes, but its role has remained enigmatic. This study establishes a...WW…

Edited by Arieh Warshel, University of Southern California, Los Angeles, CA, and approved January 26, 2021 (received for review August 13, 2020)Ion selectivity is a fundamental property of ion channels. Potassium channels exhibit an unusual selectivity, allowing passage of larger K+ ions (ionic radius of 1.3 Å) over smaller Na+ ions (1.0 Å); the mechanism underlying the small ion rejecting selectivity remains unknown. Here, we applied Na+ as a probe for examining the pore of a prototypical potassium channel and found slight Na+ conduction across the pore. Na+ traced a tortuous trajectory in...…Edited by Arieh Warshel, University of Southern California, Los Angeles, CA, and approved January 26, 2021 (received for review August 13, 2020)Ion selectivity is a fundamental property of ion channels. Potassium channels exhibit an unusual selectivity, allowing passage of larger K+ ions (ionic radius of 1.3 Å) over smaller Na+ ions (1.0 Å); the mechanism underlying the small ion rejecting selectivity remains unknown. Here, we applied Na+ as a probe for examining the pore of a prototypical potassium channel and found slight Na+ conduction across the pore. Na+ traced a tortuous trajectory in...WW…