Abstract:
The year 2020 has seen a major and sustained outbreak
of a novel betacoronavirus (severe acute respiratory
syndrome (SARS)-coronavirus
(CoV)-2) infection that
causes fever, severe respiratory illness and pneumonia,
a disease called Covid-19. At the time of writing, the
death toll was greater than 120 000 worldwide with
more than 2 million documented infections. The genome
of the CoV encodes a number of structural proteins that
facilitate cellular entry and assembly of virions, of which
the spike protein S appears to be critical for cellular
entry. The spike protein guides the virus to attach to the
host cell. The spike protein contains a receptor-binding
domain (RBD), a fusion domain and a transmembrane
domain. The RBD of spike protein S binds to Angiotensin
Converting Enzyme 2 (ACE2) to initiate cellular entry.
The spike protein of SARS-CoV-
2 shows more than
90% amino acid similarity to the pangolin and bat
CoVs and these also use ACE2 as a receptor. Binding
of the spike protein to ACE2 exposes the cleavage sites
to cellular proteases. Cleavage of the spike protein by
transmembrane protease serine 2 and other cellular
proteases initiates fusion and endocytosis. The spike
protein contains an addition furin cleavage site that may
allow it to be ’preactivated’ and highly infectious after
replication. The fundamental role of the spike protein in infectivity suggests that it is an important target for
vaccine development, blocking therapy with antibodies
and diagnostic antigen-based
tests. This review briefly
outlines the structure and function of the 2019 novel
CoV/SARS-CoV-
2 spike protein S.
