Biology Reference
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can be obtained. The
(HPV) vaccine Gardasil (VLPs of
HPV) is produced in yeast expression system (Merck & Co Inc., Whitehouse
Station, NJ, USA).
Human papilloma virus
Figure 3.4
Cryo-electron microscopy reconstructions of the SubE CCMV mutant
VLP produced in yeast (deleted N-terminus) (A) and wild-type CCMV produced in
plants (B) showing the structural similarity between the particles. Reproduced with
permission from Brumfield, S., Willits, D., Tang, L., Johnson, J. E., Douglas, T., and Young,
M. (2004) Heterologous expression of the modified coat protein of
Cowpea chlorotic
mottle bromovirus
results in the assembly of protein cages with altered architectures
and function.
J, Gen. Virol.
,
85
(Pt 4), 1049-1053.
Yeast expression of VLPs is highly flexible and allows production of mutant
particles that are unlikely to self-assemble in the natural host
. As a
proof of concept, three general classes of coat protein modifications were
introduced into CCMV that altered the interior of the capsid, the interface
between adjacent coat protein subunits, or the exterior capsid surface. VLPs
were expressed in
in vivo
, 2004). The modifications
were designed to: (i) alter the interior surface charge of the N-terminus
of the coat protein, which is the nucleic acid binding region, (ii) delete
the N-terminus, (iii) insert a peptide into a surface loop, and (iv) modify
interactions between viral coat protein subunits by altering the metal-
binding sites. As all modifications have effects on viral assembly and nucleic
acid packaging, it is unlikely that any of these mutants would assemble into
intact particles in the natural host. Expression in yeast yielded VLPs that
were indistinguishable from plant-derived wild-type particles. Empty VLPs
as well as nucleic acid-containing particles were produced and isolated in
high yields (the nucleic acid is derived from the host). Capsid proteins with
altered N-termini assembled into empty particles only; and mutant with
deleted N-terminus formed particles with a range of sizes (Figs 3.3 and 3.4)
(Brumfield
P. pastoris
(Brumfield
et al.
et al.
, 2004).
.. Baculovirus-Based expression System
Baculoviruses are insect viruses with large double-stranded DNA genomes
that can accommodate multiple foreign genes of interest. Baculoviruses
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