Environmental Engineering Reference
In-Depth Information
activate. transcription. of. Cup1. and. Crs5. metallothioneins. (Thiele. 1988,.
Culotta. et. al.. 1994),. as. well. as. the. SOD1. enzyme. (Gralla. et. al.. 1991). in. the.
presence.of.copper.
CopperTransportProteinsacrossAutotrophicModels
Copper Transport in Photosynthetic Cyanobacteria and Algae
The. photosynthetic. machinery. and. process. in. cyanobacteria. is. similar. to.
plants,. especially. under. suficient. copper. conditions.. Therefore,. studying.
the.mechanisms.and.regulation.of.copper.within.cyanobacteria.can.help.to.
understand.chloroplastic.homeostasis.in.higher.plants..Cyanobacteria.con-
tain.internal.thylakoid.membranes,.which.are.the.site.of.electron.transport..
There.are.two.major.targets.for.copper.within.cyanobacteria,.plastocyanin.
(PC). and. cytochrome.oxidase. (CO),. which.are. both. found. in.the.thylakoid.
(Figure.13.6).(Dworsky.et.al..1995,.Kerield.and.Krogmann.1998)..In.an.envi-
ronment.deprived.of.copper,.some.cyanobacteria.can.use.the.iron.contain-
ing.cytochrome.
c
6
.protein.as.a.terminal.electron.acceptor.in.photosynthesis.
instead. of. the. copper-requiring. protein. plastocyanin. (Zhang. et. al.. 1992)..
Copper.is.transported.through.the.cell.membrane.and.the.thylakoid.mem-
brane.by.two.P-type.ATPases.called.CtaA.and.PacS,.respectively.(Kanamaru.
et.al..1994,.Phung.et.al..1994)..A.copper.chaperone.similar.to.the.yeast.ATX.
protein. has. been. identiied. in. the. model. organism.
Synechocystis
. PCC. 6803.
that. interacts. in. bacterial. 2-hybrid. experiments. with. both. P-type. ATPase.
transporters. (Tottey. et. al.. 2002).. This. suggests. that. once. copper. enters. the.
cell.through.CtaA.it.is.shuttled.to.PacS.via.ATX1.in.the.cytoplasm,.for.plasto-
cyanin.or.cytochrome.oxidase.targets.
CO
PC
PacS
ATX1
Cu(l)
CtaA
FIGURE 13.6
Copper.homeostasis.in.the.cyanobacterial.model,.
Synechocystis
.(solid.line.depicts.interactions.
demonstrated.through.experimental.data,.gray.rectangles.are.copper.transporters,.and.white.
circles.represent.copper.targets).
Search WWH ::
Custom Search