Overview of the Manifold VNPs Used in Nanotechnology - Viral Nanoparticles: Tools for Materials Science and Biomedicine - page 21

Most virus capsids consist of identical copies of coat
proteins. However, there are also capsids that are formed by several different
coat proteins. In

The P numbers.

(CPMV) two different coat proteins form
the capsid, the small (S) and large (L) coat protein subunits. The S protein
is a one-domain (A domain) and the L protein is a two-domain protein (B
and C domains). The three domains can be arranged in so-called

Cowpea mosaic virus

pseudo -

equivalence. The T numbers are assigned as pseudo T or P numbers. CPMV

has = 3 symmetry and consists of 60 copies of each coat protein subunit

(Fig. 2.6; Lin, T., Chen, Z., Usha, R., Stauffacher, C. V., Dai, J. B., Schmidt, T., and
Johnson, J. E. (1999) The refined crystal structure of cowpea mosaic virus at
2.8 Å resolution,

P

(1), 20-34.).
Tuning capsid symmetry using nanotechnology.

Virology , 265

Nanotechnology
has been applied as a technique to understand virus assembly. In particular,
synthetic nanoparticles can be used as cores to nucleate assembly of BMV
particles (Chen et al ., 2006; Dixit et al ., 2006; Dragnea et al ., 2003; Sun et

al ., 2007) (see Chapter 5). Assessing whether the morphology of the capsid

could be tuned using different-sized nanoparticle cores, it was found that
the capsid symmetry indeed is dependent on the nanoparticle core size.
Incorporated gold cores of 9 nm yielded particles similar to pseudo T = 2

symmetry, = 1 symmetry, and

particles with cores of a size of 12 nm resulted in particles similar to native
particles with

1

particles with gold cores of 6 nm size showed T

., 2007). Studies along these lines are
expected to provide further insights into the fundamental understanding of
viral self-assembly.

T = 3 symmetry (Sun et al

2.1.2.2 Rod-shaped VNPs: helical tubes and ilamentous structures

Icosahedral particles are relatively more common than rod-shaped or
filamentous structures. There are, however, a number of rod-shaped particles
relevant to nanotechnology including:

Tobacco mosaic virus (TMV), Potato

virus X (PVX), M13, and Sulfolobus islandicus rod-shaped virus 2 (SIRV2) (for

example, see references: Carette et al ., 2007; Lee et al ., 2009; Mao et al ., 2004;

Nam et al ., 2006, 2008; Schlick et al ., 2005; Shenton et al ., 1999; Steinmetz et

al ., 2008; Tseng et al ., 2006; Yi et al ., 2007; Yoo et al ., 2006).

1

T = 2 symmetry is typically referred to as pseudo T = 2 symmetry. According to the model by

Kasper and Klug (see Eq. 1), a = 2 would not be feasible. However, proteins and potein-protein

interactions are flexible — also allowing symmetries that would not have been predicted using
mathematical models.

T