Handling Copper: A Paradigm for the Mechanisms of Metal Ion Homeostasis - Environmental Contamination: Health Risks and Ecological Restoration - page 272

(Histidine)

N

Methionine?

N

S

(Histidine)

(Cysteine)

S S

S

(Cysteine)

(A) (Methionine) (B) (Cysteine)

FIGURE 13.3
Diagrams.depicting.copper.coordinating.sites.in.the.blue.copper.binding.protein,.plastocyanin.
(A),. and. possible. copper. binding. sites. in. copper. transporters. and. chaperones. containing. an.
MxCxxC.heavy.metal.domain.(B).

O'Halloran.2000)..Structure.analysis.of.the.yeast.ATX1. bound.with.Hg(II).
and.a.domain.of.the.Menkes.disease.protein.(Mnk4).bound.with.Ag(I).indi-
cate.that.the.conserved.methionine.residue.is.not.in.close.enough.proximity.
to.interact.with.the.metal.ion.(Gitschier.et.al..1998,.Rosenzweig.et.al..1999)..
In.yeast.2-hybrid.experiments.it.has.been.observed.that.when.several.con-
served.lysine.residues.located.near.the.MxCxxC.domain.are.mutated.in.the.
yeast.ATX1.copper.chaperone.it.loses.interaction.with.the.Ccc2.transporter.
(Portnoy.et.al..1999)..This.implies.that.these.lysines.are.necessary.for.the.two.
proteins.to.interact.with.each.other.or.alters.the.conformation.of.the.metal.
binding.pocket.

CopperTransportProteinsacrossHeterotrophicModels
Since.many.aspects.of.copper.homeostasis.are.conserved.across.organisms,.
the.following.sections.are.a.review.of.what.is.known.about.copper.trafick-
ing.across.selected.model.systems:.bacteria,.yeast,.cyanobacteria,.and.plants..
For.a.complete.list.of.copper.traficking.proteins.and.targets.in.these.various.
organisms,.please.refer.to.Tables.13.1.through.13.4.

Bacterial Copper Transport Mechanisms

Many.of.the.transporters,.copper.chaperones,.and.target.enzymes.for.cop-
per. present. in. E. coli . can. be. found. in. other. prokaryotes,. as. well. as. more.
complex. eukaryotic. systems.. Enterococcus hirae . is. one. model. organism. for.
researching.copper.transport.in.a.prokaryotic.system,.as.a.result.it.is.vastly.
studied. and. well. understood. (Lu. et. al.. 2003,. Solioz. and. Stoyanov. 2003,.
Magnani.and.Solioz.2005)..These.Gram-positive.bacteria.contain.two.P-type.
ATPase. transporters,. located. in. the. plasma. membrane,. that. function. in.
copper.transport.(Figure.13.4A).(Odermatt.et.al..1993,.1994)..The.expression.
of.both.CopA.and.CopB.transporters.are.inducible.under.high.extracellular.