Strong evolutionary convergence of receptor-binding protein spike between COVID-19 and SARS-related coronaviruses

Yonghua Wu

Given the positive selection of the S gene in both branches, C and K, we further examined its positive selection signals using branch-site model along all other main branches ( Fig. 1) to test whether the positive selection uniquely occurred along the branches related to 2019-nCoV and SARS-CoV. Our results showed positive selection signals along 10 out of 45 branches examined (Fig. 1, Table S3 ). This may suggest that the S gene was widely subject to Darwinian selection in different coronavirus strains, indicating that it may be crucial for the successful survival of coronaviruses. Further analyses of positive selection sites showed that most positive selection sites among all 12 branches under positive selection were located within subunit 1 of S gene ( Table 1, Table S3 ), which is used for receptor binding. This may suggest that there are strong selection pressures of different coronavirus strains for their own receptor binding.