In a second approach, four proteins that participate in the entry of SARS-CoV-2 into host cells (i.e., the two viral proteins S protein and protein 7a as well as the two human host cell proteins ACE2 and TMPRSS2) were predicted as potential heme-binding proteins (out of six analyzed COVID-19-related proteins). The gene discussed is TMPRSS2; the disease is COVID-19.