Biomedical Engineering Reference
In-Depth Information
segments. in. each. virus. particle. remains. a. mystery.. There. remains. a. distinct. possibility.
that.researchers.have.to.yet.identify.all.the.nucleoprotein.interactions.that.occur.in.each.
virus.system.(Knipe.et.al..2007).
7.1.3 Virus engineering
It.is.only.within.the.last.20.years.that.the.concept.of.engineering.viruses.for.other.purposes.
began. to. appear. in. the. scientiic. literature. (with. the. exception. of. vaccine. development)..
The.irst.attempts.typically.involved.genetic.modiication.of.the.virus.protein.coat.with.the.
purpose.of.presenting.peptides..In.1998,.a.seminal.study.by.Trevor.and.Douglas.published.
in. Nature. demonstrated. inorganic. materials. synthesis. inside. the. capsid. of. cowpea.
chlorotic. mottle. virus. (Douglas. and. Young. 1998).. The. following. year,. the. same. group.
published.an.additional.study.involving.nucleation.of.additional.inorganic.materials.on.
the.capsid.exterior.of.tobacco.mosaic.virus.(Shenton.et.al..1999)..In.our.opinion,.these.two.
studies. mark. the. birth. of. the. ield. of. viral. nanobioengineering.. Within. 3. years,. a. host.
of.engineering.and.modiication.approaches.were.published.on.a.slew.of.different.virus.
systems.with.potential.applications.ranging.from.drug.delivery.to.nanoelectronics.
The.six.virus.systems.discussed.in.this.chapter.are.the.most.investigated.and.engineered.
systems. up. to. this. point,. and. provide. examples. of. many. areas. in. which. the. use. of. viral.
nanobioengineering. can. potentially. have. a. major. impact.. The. virus. systems. that. will. be.
discussed. are:. cowpea. chlorotic. mottle. virus. (CCMV),. tobacco. mosaic. virus. (TMV),. M13.
bacteriophage,. MS2. bacteriophage,. cowpea. mosaic. virus. (CPMV),. and. red. clover. necrotic.
mosaic.virus.(RCNMV),.and.are.shown.in.Figure.7.2..Please.note.that.there.are.several.other.
viruses.that.have.on.occasion.been.explored.for.use.in.this.burgeoning.ield..However,.we.
deem.that.the.chosen.systems.provide.a.good.overall.representation.of.the.vast.majority.of.
work.done.up.to.this.date..Viruses.are.unique.biological.systems.that.have.evolved.a.vast.
array.of.functions.and.forms.while.retaining.a.minimal.amount.of.genetic.information.in.
the.process..The.ield.of.viral.nanobioengineering.is.relatively.new,.and.the.potential.to.take.
advantage.of.these.streamlined.nanomachines.is.only.beginning.to.come.into.view.
7.2 Cowpea Chlorotic Mottle Virus
7.2.1 general Properties, Structure, and Assembly
The.cowpea.chlorotic.mottle.virus.(CCMV).is.a.plant.virus,.belonging.to.the.
Bromoviridae
.
family..It.was.the.irst.icosahedral.virus.to.be.reassembled.in.vitro.from.puriied.capsid.
protein.and.isolated.RNA.to.create.a.biologically.active.virion.(Bancroft.and.Hiebert.1967a)..
CCMV. has. an. icosahedral. (T.=.3). capsid. structure. made. of. 180. identical. coat. proteins.
clustered.into.20.hexameric.and.12.pentameric.units.to.produce.an.∼29.nm.diameter.capsid..
Four.different.positive.sense.single-stranded.RNA.molecules.(RNA.1-4).are.encapsulated.
into.three.unique.virions.with.similar.structure..RNA.3-4.is.copackaged.into.one.virion.
and.encodes.for.the.movement.and.coat.protein,.respectively..The.coat.protein.is.19.8.kDa.
and. consists. of. a. β-barrel. fold. where. a. 50. amino. acid. N-terminus. protrudes. from. one.
end.and.a.14.residue.C-terminus.extends.in.the.opposite.direction.(Speir.et.al..1995)..The.
initial.portion.of.the.N-terminus.is.highly.positively.charged.and.extends.into.the.capsid.
where.it.binds.and.helps.in.neutralizing.the.charge.of.the.packaged.RNA.(Zhao.et.al..1995)..
