ISBN: 978-83-60043-10-3 - eurobic9

Eurobic9, 2-6 September, 2008, Wrocław, Poland
KL12. Copper Resistance in E. coli. The Multicopper Oxidase PcoA
Catalyses Oxidation of Copper(I) in Cu I Cu II -PcoC.
Control of Seven Copper Sites in a Single Catalytic Reaction.
K.Y. Djoko, M. Zimmermann, L.X. Chong, Z. Xiao, A.G. Wedd
School of Chemistry and Bio21 Research Institute, University of Melbourne, Parkville, Victoria 3010, Australia
PcoA and PcoC are two of the soluble proteins expressed to the periplasm as part of the copper resistance
response of E. coli. PcoC binds both copper(I) and copper(II) to form air-stable Cu I Cu II -PcoC. The blue
multicopper oxidase PcoA is shown to catalyze oxidation of copper(I) bound in Cu I Cu II -PcoC to less toxic
copper(II) which is released into solution (Figure) [2] This is consistent with a role for PcoA as a cuprous
oxidase. These two proteins may interact with the outer membrane protein PcoB to export excess copper from
the periplasm.
Figure. The binding modes of copper and their affinities in these systems will be compared with:
(a) N-terminal domains of copper and zinc transmembrane transporters HMA2, 4 and 7 from the simple plant
Arabidopsis thaliana: the HMA4 domain binds Cu + with 10 6 higher affinity than it binds Zn 2+ , its putative
substrate [2].
(b) the chaperone protein CopK from the bacterium Cupriavidus metalliduran CH34: remarkably, binding of
Cu(I) in a [Cu(S-Met)4] + site induces cooperative binding of Cu(II). The affinity for Cu(II) increases by a factor
of 10 6 upon binding of Cu(I) [3].
References:
[1] K.Y. Djoko, Z. Xiao, A.G. Wedd, ChemBioChem 2008, in press.
[2] M. Zimmermann, Z. Xiao, A. G. Wedd et al 2008, submitted for publication.
[3] L. X. Chong, M. J. Maher, M. G. Hinds, Zhiguang Xiao and Anthony G. Wedd 2008, submitted for
publication.
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