A team of scientists at the U.S. Department of Energy's (DOE) Brookhaven National Laboratory and Columbia University has demonstrated a way to produce large quantities of the receptor that SARS-CoV-2, the virus that causes COVID-19, binds to on the surface of human cells. That binding between the now-infamous viral spike protein and the human "ACE2" receptor is the first step of infection by the virus. Making functional human ACE2 protein in mouse cells gives scientists a new way to study these receptors and potentially put them to use. In addition, as described in a paper just published in the journal Virology, the method could facilitate the study of other complex proteins that have proven difficult to produce by other means.