The current pandemic disease (COVID-19) is caused by a highly infectious
coronavirus known as severe acute respiratory syndrome coronavirus 2 (SARS-Co-
-2). It belongs to the family of Coronaviridae, subfamily Orthocoronaa-virinae, order
Nidovirales. Coronaviruses (CoVs) are enveloped and spherical shaped pathogens with
crown-like protrusions formed by S protein on the surface. The CoVs contain singlestranded
positive-sense RNA with genome of 27-32 kb that encodes both structural and
non-structural proteins. The Coronavirus genome encodes for at least 6 ORFs, among
which two third parts include ORF 1a/1b, which encodes 16 non-structural proteins
(nsp 1-16) that play a pivotal role in viral genome replication. The structural proteins
are part of mature virion and include spike (S), envelope (E), membrane (M) and
nucleocapsid (N) proteins. The S protein binds to the receptor (ACE2 or others) on the
host cell and determines host tropism. Replication of CoVs is extremely complicated
process and includes regulation at various stages including dependency on both the
viral and host factors. The present chapter provides updated information about the
morphology, genomic structure, properties and function of different proteins and their
role in replication mechanism of SARS-CoV-2. The information about the proteins and
their role in viral life cycle is likely to assist in the formulation of targeted therapeutic
interventions and vaccines against this emerging respiratory pathogen.
Keywords: COVID-19, Genome, Morphology, Proteins, Replication, SARSCoV-
2.
