Molecular analysis of binding region of an ACE2 as a receptor for SARS-CoV-2 between humans and mammals

In June 2020, a second wave of coronavirus disease-2019 (COVID-19) infections raised concern in Beijing, where salmon sold a fresh fish wholesale market was suspected of being the source of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections. It has raised questions in the press and elsewhere about the scientific basis of salmon as a source of infection. With the number of cases growing, the surface of a salmon chopping board in the market was examined for the presence of SARS-CoV-2 and a positive reaction was observed. Following these test results, there has been debate over whether salmon can be infected with SARS-CoV-2. To find assess this, we investigated the structural homology of angiotensin-converting enzyme 2 (ACE2), a host-side receptor for SARS-CoV-2, between humans and other species including salmon and mink. As a result, a high structural homology between ACE2 and mink, which has reportedly transmitted SARS-CoV-2 to humans, was confirmed. However, a non-high structural homology of ACE2 between salmon and humans was observed. Further experiments are needed to find the source of SARS-CoV-2 transmission to the salmon.