Evidence of the Recombinant Origin and Ongoing Mutations in Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2)

Jiao-Mei Huang; Syed Sajid Jan; Xiaobin Wei; Yi Wan; Songying Ouyang

The amino acid residues change in S-protein of SARS-CoV-2 was further analyzed with SARS-CoV, pangolin and bat CoVs including pangolin/Guandong/1/2019, pangolin/Guangdong/lung08, and bat/Yunnan/RaTG13 (Figure 2) . Regardless of low homology between SARS-CoV-2 (Wuhan-Hu-1_MN908947) and SARS-CoV (SARS_AAR07630), they had many homologues areas in S-protein. The five key amino acid residues of S-protein at positions 442,472, 479,480, and 487 of SARS-CoVs are described to be at the angiotensin-converting enzyme-2 (ACE2) receptor complex interface and supposed to be crucial for human to human and cross-species transmission (Li et al., 2005b; Wu et al., 2012) . Figure 2b and Table S1 describe that all key amino acid residues of RBD (except two positions) are completely homologues between SARS-CoV-2 (Wuhan-Hu-1_MN908947) and pangolin CoVs (pangolin/Guandong/1/2019 and pangolin/Guangdong/lung08), supporting our postulation of recombination event in S-protein gene. Even though, all five crucial amino acid residues of SARS-CoV-2 for binding to ACE2 are different from SARS-CoV, their hydrophobicity and polarity are similar, having same S-protein structural confirmation and identical RBD 3-D structure (Xu et al., 2020) . In addition, six critical key residues in MERS-CoV RBD binding to its receptor dipeptidyl peptidase 4 (DPP4) are all different in SARS-CoV and SARS-CoV-2 related coronavirus (Figure 2a) .