The hull of the virus is made up of a double membrane of lipids (shown in grey) from the host cell in which the virus was made.
The water-loving (hydrophilic) parts of the lipids face outside, while the water-adverse (hydrophobic) parts face to the inside of the membrane. This arrangement easily explains why the virus can be destroyed by soap: soap dissolves bi-lipidic membranes.
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In addition to the Spike protein, there are two more proteins embedded in the bilipidic membrane, the membrane protein and the envelope protein.
The membrane protein plays an important role in the assembly of the viral macromolecules in the host cell (Ensuring everything is packed correctly to be functional). To date no atomic structure has been determined of the membrane protein.
The small envelope (E) protein also appears to play a major role in the formation of virions. Without the E protein, fewer viruses are produced and are less virulent. The E protein forms pentameric pores in the host cell membranes which act as ion transporters (yellow) – if they actually exist on the viral hull is unclear.
