Biology Reference
In-Depth Information
VLP formation.
25,26,32
However, further deletion of the N terminus
affected assembly, indicating that the N terminal region is a molecular
switch that contains determinates for assembly.
VP1: S Domain
The contiguous shell is formed from the closely interacting S domains
of the 180 capsid proteins. The S domain is composed of residues
50 to 225 and is relatively conserved among caliciviruses. In the Norwalk
virus, the S domain folds into eight-strand antiparallel
β
-barrel
structures.
28
This eight-strand antiparallel
β
-barrel is a common cen-
tral structural motif in the T
3 plant and insect viruses. One study
suggested that all caliciviruses exhibit this eight-strand antiparallel
=
-
barrel structure and that it is the most conserved structural feature in
the calicivirus structures.
29
And another study showed that expression
of the S domain alone resulted in the formation of smooth particles,
but deletion of part of the S domain resulted in the formation of
unstable particles, indicating that the S domain contained all the
determinates, or a scaffold, for assembly.
6
The Norwalk virus shell lies
between radii of 110 and 150 Å.
β
VP1: P1 Subdomain
The S domain is connected to the P1-1 by a flexible hinge. For the
Norwalk virus, the P1 subdomain consists of residues 226 to 278
(called P1-1) and 406 to 520 (called P1-2). The P1-1 subdomain
contains three
β
strands, whereas the P1-2 subdomain contains six
helix.
28
Comparison studies of NoV genogroup I
and II VLP cryo-EM structures found that the P1-1 and P2 subdo-
mains were involved in the intradimeric interactions, whereas for SaV
and vesivirus, only the P2 subdomain was thought to be involved in
the intradimeric interactions and the P1 domain was involved in the
interdimeric interaction.
29
Amino acid alignments, secondary struc-
ture predictions, and fitting models have indicated that the P1 sub-
domain is conserved in all caliciviruses.
29
β
strands and an
α
