Bats and pangolins are considered to be potential hosts of the new coronavirus SARS-CoV-2, based on its genome similarity to coronaviruses of these species (Bat-CoV-RaTG13 and Pangolin-CoV). The receptor-binding domain (RBD), a functional component of the spike protein, is responsible for binding of SARS-CoV-2 by human ACE2 receptors and is also key to cross-species viral transmission. We performed molecular dynamics (MD) simulations using structures of hACE2 in complex with the RBD of SARS-CoV-2, SARS-CoV, Pangolin-CoV and Bat-CoV-RaTG13, respectively. By analyzing the hydrogen-bonding network at the RBD-hACE2 interface and estimating the binding free energies between RBD and hACE2, we found Pangolin-CoV bound hACE2 in a similar state as did SARS-CoV-2, and both of them bound hACE2 more strongly than did Bat-CoV-RaTG13 or SARS-CoV. We further identified two major adaptation mutations of SARS-CoV-2-RBD, which may have significant roles in regulating the recognition and binding between RBD and hACE2. Our results add to existing evidence that Pangolins have the potential to act as an intermediate host for SARS-CoV-2, and provide guidance for future design of antiviral drugs and vaccines.
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