Biology Reference
In-Depth Information
feedback from the community. We invite and welcome participation of
the community at all levels of our efforts, from helping us better curate
specific information of specific genomes to suggestions of tools that
can help the community better take advantage of the wealth of infor-
mation available on our website. There are specific mechanisms for
feedback at our website (http://patric.vbi.vt.edu), and comments can
also be sent to the e-mail address patric@vbi.vt.edu.
Viruses Curated at PATRIC
This section offers an introduction to each of the five viral Patho-
Systems that are being curated at PATRIC. Current knowledge of the
taxonomy, structure, and host-range of each PathoSystem are briefly
described.
The Genus Coronavirus
The genus
coronavirus
is a member of the family
Coronaviridae
.
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Coronaviruses are large, enveloped, single-stranded, positive-sense
RNA viruses. With genome sizes ranging from 27 to 32 kB, the coro-
naviruses have the largest genomes of all the known RNA viruses.
They have a spherical lipid-bilayer envelope enclosing a nucleocapsid
core. The lipid envelope has multiple copies of the integral M (mem-
brane) and S (spike) glycoproteins, the latter protruding outwards in
the form of club-shaped spikes. Some coronaviruses (belonging to
Group 2, see below) possess a third integral membrane glycoprotein:
HE (hemagglutinin-esterase) protein. The genomic RNA molecule,
which is capped and polyadenylated, associates with copies of the N
(nucleocapsid) protein to form a long, helical nucleocapsid. A typical
coronavirus genome has two large, overlapping open-reading frames
(ORF), ORF1a and ORF1b, that encode two polyproteins, and a set
of ORFs that encode structural (S, M, N) and other accessory pro-
teins. While all coronaviruses encode the two polyproteins, the num-
ber and composition of the other ORFs vary between species.
Coronaviruses are found in birds and mammals. The viruses
fall into three categories, based on serological cross-reactivity:
