ABSTRACT
A novel disease, COVID-19, is sweeping the world since end of 2019. While in many countries, the first wave is over, but the pandemic is going through its next phase with a significantly higher infectability. COVID-19 is caused by the novel Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) that seems to be more infectious than any other previous human coronaviruses. To understand any unique traits of the virus that facilitate its entry into the host, we compared the published structures of the viral spike protein of SARS-CoV-2 with other known coronaviruses to determine the possible evolutionary pathway leading to the higher infectivity. The current report presents unique information regarding the amino acid residues that were a) conserved to maintain the binding with ACE2 (Angiotensin-converting enzyme 2), and b) substituted to confer an enhanced binding affinity and conformational flexibility to the SARS-CoV-2 spike protein. The present study provides novel insights into the evolutionary nature and molecular basis of higher infectability and perhaps the virulence of SARS-CoV-2.