3.4. Envelope protein (E protein)
The E proteins of SARS-CoV-2, SARS-CoV, and BatCoV RaTG13 are consisted
of 75, 76, and 75 amino acids, respectively (Table 1). The identity and
similarity percentages of the E protein of SARS-CoV-2 and SARS-CoV are
94.7 and 96.1 compared to 94.7 and 97.4 of Yashimito (2020) [12]
(Table.2). The E proteins of the SARS-CoV-2 and the BatCoV RaTG13 are
100% identical and similar. The results strongly favor the bat origin
of SARS-CoV-2 over the SARS-CoV origin. The E protein contains three
domains; C-terminal, N- terminal, and trans-membrane with different
functions for the virus and in the host cells [30].
The E protein plays different functions for the viral replication and
for the interaction of the virus with the host organisms and cells such
as the assembly of the virion envelope; suppression of the host cells
stress responses; facilitation of the viral replication and vitality;
and acting as ion channel to induce the release of the virions from the
host cells [31-35].