Biology Reference
In-Depth Information
Fig. 1.
-trace of the core structure.
The icosahedrally independent molecules P3A and P3B are shown in light
blue and pink, respectively. Notations of individual P3 proteins are also
shown (the letters A and B denote icosahedrally independent molecules).
(b)
C
Structure of
Rice dwarf virus
.
2
(a)
C
α
-trace of the outer shell of RDV. Each icosahedral asymmetric unit
contains 13 copies of P8 proteins, designated P, Q, R, S, and T and colored
red, orange, green, yellow, and blue, respectively. The representations were
generated using MOLSCRIPT
24
and rendered with RASTER3D.
25
α
composed of P8-trimers (Fig. 2(a)), which we have designated P, Q,
R, S and T, respectively (Fig. 1(b)).
It is noteworthy that the core capsid protein P3 is very thin (along
the “z” axis) varying from 25 to 45 Å in thickness, but it covers a
relatively wide area of 65
150 Å (Fig. 3(a)). The atomic structures
of the innermost first-layer capsid proteins of BTV
3
and orthore-
ovirus
4
are basically the same as that of P3 of RDV (Figs. 3(b) and
3(c)). These proteins seem to have the ability to generate the spacious
cavity within the viral core. However, this type of structure implies
that side-by-side binding of the proteins must be very weak because
of the small area of the face of each that interacts with others. Our
group found that expression of the core capsid protein P3 of RDV
in a baculovirus system resulted in the formation of single-layered
core-like particles in insect cells in the absence of any other capsid
proteins,
7
indicating that P3 has the intrinsic ability to form core
particles. Thus, P3 appears to have the conformational properties
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