eLife assessment
The function of specific proteins made by SARS-CoV-1 and SARS-CoV-2 is under debate, with diverging claims previously published regarding the ability of Orf3a proteins from either virus to form ion channels. The authors undertook a thorough characterization of Orf3a from CoV-1 and CoV-2 by combining data from a range of different structural and functional experiments, arguably providing the most compelling evidence to date that Orf3a from viruses is not an ion channel. Instead, the orthologue-specific interaction with a component of a larger protein complex suggests a role of one of the two membrane proteins in the endo-lysosomal pathway. The work is significant from a fundamental science perspective, for its implications for COVID antiviral development strategies, and also for establishing guidelines for future identification of true viral ion channels.