Making the leap from structure to mechanism: are the open states of mammalian complex I identified by cryoEM resting states or catalytic intermediates?

Respiratory complex I (NADH:ubiquinone oxidoreductase) is a multi-subunit, energy-transducing mitochondrial enzyme that is essential for oxidative phosphorylation and regulating NAD+/ NADH pools. Despite recent advances in structural knowledge and a long history of biochemical analyses, the mechanism of redox-coupled proton translocation by complex I remains un-known. Due to its ability to separate molecules in a mixed population into distinct classes, single-particle electron cryo-microscopy has enabled identification and characterisation of different complex I conformations. However, deciding on their catalytic and/or regulatory properties to underpin mechanistic hypotheses, especially without detailed biochemical charac-terisation of the structural samples, has proven challenging. In this review we explore different mechanistic interpretations of the closed and open states identified in cryoEM analyses of mammalian complex I.

Automated summary

In this review, we explore different mechanistic interpretations of the closed and open states identified in cryoEM analyses of mammalian complex I.