  The reason of significantly higher transmissibility of SARS Covid (2019
CoV-2) compared to SARS Covid (2003 CoV) and MERS Covid (2012 MERS) can be
attributed to mutations reported in structural proteins, and the role played by
non-structural proteins (nsps) and accessory proteins (ORFs) for viral
replication, assembly, and shedding. Envelope protein E is one of the four
structural proteins of minimum length. Recent studies have confirmed critical
role played by the envelope protein in the viral life cycle including assembly
of virion exported from infected cell for its transmission. However, the
determinants of the highly complex viral - host interactions of envelope
protein, particularly with host Golgi complex, have not been adequately
characterized. CoV-2 and CoV Envelope proteins of length 75 and 76 amino acids
differ in four amino acid locations. The additional amino acid Gly (G) at
location 70 makes CoV length 76. The amino acid pair EG at location 69-70 of
CoV in place of amino acid R in location 69 of CoV-2, has been identified as a
major determining factor in the current investigation. This paper concentrates
on the design of computational model to compare the structure/function of wild
and mutants of CoV-2 with wild and mutants of CoV in the functionally important
region of the protein chain pair. We hypothesize that differences of CAML model
parameter of CoV-2 and CoV characterize the deviation in structure and function
of envelope proteins in respect of interaction of virus with host Golgi
complex; and this difference gets reflected in the difference of their
transmissibility. The hypothesis has been validated from single point
mutational study on- (i) human HBB beta-globin hemoglobin protein associated
with sickle cell anemia, (ii) mutants of envelope protein of Covid-2 infected
patients reported in recent publications.
