Handling Copper: A Paradigm for the Mechanisms of Metal Ion Homeostasis - Environmental Contamination: Health Risks and Ecological Restoration - page 285

CCH

?

Mitochondrion

CCS ATX1

COX?

RAN1

?

CSD1

Cyt- c

?

ETR

Nucleus

Golgi

CSD3

Peroxisome

Cu(l)

?

CCS

CCP

CSD2

CutA

Chloroplast

Thylakoid

PC

Vacuole

FIGURE 13.7
Copper.transport.pathways.in. Arabidopsis thaliana .(solid.lines.depict.interactions.demonstrated.
through.experimental.data,.dashed.lines.are.hypothetical.pathways,.gray.rectangles.are.cop-
per.transporters,.and.white.circles.represent.copper.target.

Alonso.2000)..Similar.to.RAN1,.the.HMA5.membrane.transporter.is.highly.
expressed. in. roots. and. lowers,. but.based. on. mutant. analysis. the. function.
seems.to.be.copper.detoxiication.in.the.roots.(Andres-Colas.et.al..2006).
Copper. chaperones. that. are. responsible. for. ion. transport. to. the. mito-
chondrion. for. cytochrome. c . oxidase. are. currently. unknown.. However,.
a. homolog. to. the. yeast. Cox17. protein. has. been. found. in. Arabidopsis . that.
may.play.a.role.in.mitochondrial.copper.delivery.(Balandin.and.Castresana.
2002).. Arabidopsis .contains.three.Cu,Zn.SOD.enzymes.located.in.the.cytosol.
(CSD1),.stroma.(CSD2),.and.peroxisome.(CSD3)..Plants.possess.a.homolog.of.
the.yeast.CCS,.also.called.CCS.that.is.the.copper.chaperone.for.SOD..There.
is. only. one. CCS . gene. in. Arabidopsis ;. however,. it. has. been. suggested. that.
several.start.sites.for.transcription.of.the.gene.result.in.different.subcellular.
locations.(Abdel-Ghany.et.al..2005a,.Chu.et.al..2005).
Within. Arabidopsis . chloroplasts. there. are. two. P-type. ATPases. similar. to.
the.RAN1.transporter..The.outer.membrane.of.the.chloroplast.is.porous.and.
many. ions,. including. copper. perhaps,. can. diffuse. readily. through. it.. One.
of. the. P-type. ATPases,. PAA1,. has. been. localized. to. the. membrane. (inner).
of.the.chloroplast.(Shikanai.et.al..2003)..The.second.transporter,.PAA2,.has.
been.localized.using.GFP.(Green.Fluorescent.Protein).to.the.thylakoid.mem-
brane. (Abdel-Ghany. et. al.. 2005b).. The. PAA1. and. PAA2. proteins. are. func-
tional. homologs. of. the.CtaA.and.PacS,.respectively,.in. cyanobacteria..Both.
of. the. PAA. transporters. contain. a. heavy. metal. binding. motif,. MxCxxC,. at.
the. N-terminal. domain. of. the. peptide. along. with. the. chloroplastic. transit.