Affinity enhancement of CR3022 binding to RBD; site directed mutagenesis using molecular dynamics simulation approaches.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a disease which caused by a novel beta coronavirus. Structural and non-structural proteins are expressed by the virus gene fragments. The RBD of the S1 protein of the virus has the ability to interact with potent antibodies including CR3022, which was characterized to target the S protein of the virus which can efficiently neutralize the SARS-CoV and . In current study, we aimed to design CR3022 based antibody with high affinity compared with wild-type CR3022 using MD simulation method. Two variants were designed based on the amino acid binding conformation and the free binding energy of the critical amino acids which involved in CR3022-RBD interactions were evaluated. In this study three complexes were evaluated; CR3022-RBD, V1-RBD and V2-RBD using molecular dynamics simulations carried out for 100 ns in each case. Then, all the complexes were simulated for 100 ns. In the next step, to calculate the free binding affinity of the wild CR3022 and mutant antibody (V1 and V2) with RBD, the PMF method was performed. The RMSD profile demonstrated that all three complexes were equilibrated after 85 ns. Furthermore, the free binding energy results indicated that the V2-RBD complex has the higher binding affinity than V1-RBD and CR3022-RBD complexes. It should be noted that in above variants, the electrostatic energy and the number of H-bonds between the antibody and RBD increased. Thus, it is suggested that both designed antibodies could be considered as appropriate candidates for covid-19 disease treatment.Communicated by Ramaswamy H. Sarma.