ORF3b is a gene found in coronaviruses of the subgenusSarbecovirus, encoding a short non-structuralprotein. It is present in both SARS-CoV (which causes the disease SARS) and SARS-CoV-2 (which causes COVID-19), though the protein product has very different lengths in the two viruses. The encoded protein is significantly shorter in SARS-CoV-2, at only 22 amino acid residues compared to 153–155 in SARS-CoV.[1][2] Both the longer SARS-CoV and shorter SARS-CoV-2 proteins have been reported as interferon antagonists.[2] It is unclear whether the SARS-CoV-2 gene expresses a functional protein.[3]
