Sequence and structural analysis of COVID-19 E and M proteins with MERS virus E and M proteins-A comparative study.

The outbreak of SARS in 2003, MERS in 2012, and now COVID-19 in 2019 has demonstrated that Coronaviruses are capable of causing primary lethal infections in humans, and the pandemic is now a global concern. The COVID-19 belongs to the beta coronavirus family encoding 29 proteins, of which four are structural, the Spike, Membrane, Envelope, and Nucleocapsid proteins. Here we have analyzed and compared the Membrane (M) and Envelope (E) proteins of COVID-19 and MERS with SARS and Bat viruses. The sequence analysis of conserved regions of both E and M proteins revealed that many regions of COVID-19 are similar to Bat and SARS viruses while the MERS virus showed variations. The essential binding motifs found in SARS appeared in COVID-19. Besides, the M protein of COVID-19 showed a distinct serine phosphorylation site in the C-terminal domain, which looked like a catalytic triad seen in serine proteases. A Dileucine motif occurred many times in the sequence of the M protein of all the four viruses compared. Concerning the structural part, the COVID-19 E protein showed more similarity to Bat while MERS shared similarity with the SARS virus. The M protein of both COVID-19 and MERS displayed variations in the structure. The interaction between M and E proteins was also studied to know the additional binding regions. Our study highlights the critical motifs and structural regions to be considered for further research to design better inhibitors for the infection caused by these viruses.