The copper active site of CBM33 polysaccharide oxygenases

Hemsworth, Glyn R., Taylor, Ed, Kim, Robbert Q. , Gregory, Rebecca C., Lewis, Sally J., Turkenburg, Johan P., Parkin, Alison, Davies, Gideon John and Walton, Paul Howard (2013) The copper active site of CBM33 polysaccharide oxygenases. Journal of the American Chemical Society, 135 (16). pp. 6069-6077. ISSN 0002-7863

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The capacity of metal-dependent fungal and bacterial polysaccharide oxygenases, termed GH61 and CBM33
respectively, to potentiate the enzymatic degradation of cellulose opens up new possibilities for the conversion of recalcitrant
biomass to biofuels. GH61s have already been shown to be unique metalloenzymes containing an active site with a
mononuclear copper ion coordinated by two histidines, one of which is an unusual -N methylated N-terminal histidine.
We now report the structural and spectroscopic characterization of the corresponding copper CBM33 enzymes. CBM33
binds copper with high affinity at a mononuclear site, significantly stabilizing the enzyme. X-band EPR spectroscopy of
Cu(II)-CBM33 shows a mononuclear type 2 copper site with the copper ion in with a distorted axial coordination sphere,
into which azide will coordinate as evidenced by the concomitant formation of a new absorption band in the UV/vis spectrum
at 390 nm. The enzyme’s three-dimensional structure contains copper which has been photo-reduced to Cu(I) by
the incident X-rays, confirmed by x-ray absorption/fluorescence studies of both aqueous solution and intact crystals of
Cu-CBM33. The single copper(I) ion is ligated in a T-shaped configuration by three nitrogen atoms from two histidine
side chains and the amino terminus, similar to the endogenous copper coordination geometry found in fungal GH61

Additional Information:Published online March 29th 2013
Keywords:CBM33, GH61, oxidases, Copper ion
Subjects:C Biological Sciences > C700 Molecular Biology, Biophysics and Biochemistry
Divisions:College of Science > School of Life Sciences
ID Code:8829
Deposited On:09 Apr 2013 14:45

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