Abstract
Many key residues, which mediate the interaction between SARS-CoV2 spike glycoprotein (S protein) and human ACE2 receptor, have been reviewed using the SARS-CoV2 S spike protein with human ACE2 complex. The initial SARS-CoV2 S protein and ACE2 protein complex structure is formed by RBD structure of SARS-CoV2 S protein and ACE2 protein. However, the cryo-EM structure study targeting SARS-Cov S protein with human ACE2 complex has shown that there exist different binding conformations during the binding process facing ACE2 protein. It suggests the interaction between SARS-CoV2 S spike protein complex might have different binding conformations, which request full-length of SARS-CoV2 S protein complex in the structure-functional analysis. In this study, we built a full-length SARS-CoV2 S protein with human ACE2 complex by computational methods. Residues K31, H34, E35 in ACE2 protein were showed both in our full-length model and RBD structure model, which recognized as critical residues in previous studies. Surprisingly, ACE2 residues E564, R559, N556 were only found participating in the interaction of our full-length model, which suggested the full-length model has bigger binding interface. This finding was further supported by the interaction network of full-length model and RBD model. Meanwhile, the method bias was taken into consideration. Eventually, the MM-PBSA results showed the full-length model had a stronger binding free energy (almost 5-fold) than the RBD structure model of SARS-CoV2 S spike protein complex. In computational level, we present a stronger binding model containing a full-length structure of SARS-CoV2 S protein with ACE2 complex.