Journal:JBIC:22

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Catechol oxidases (EC 1.10.3.1) catalyse the oxidation of o-diphenols to their corresponding o-quinones. These oxidases contain two copper ions (CuA and CuB) within the so-called coupled binuclear type-3 copper site as found in tyrosinases (EC 1.14.18.1) and haemocyanins. We determined the first crystal structure of a fungal catechol oxidase from ''Aspergillus oryzae'' (AoCO4).
Catechol oxidases (EC 1.10.3.1) catalyse the oxidation of o-diphenols to their corresponding o-quinones. These oxidases contain two copper ions (CuA and CuB) within the so-called coupled binuclear type-3 copper site as found in tyrosinases (EC 1.14.18.1) and haemocyanins. We determined the first crystal structure of a fungal catechol oxidase from ''Aspergillus oryzae'' (AoCO4).
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Two different forms of AoCO4, called as a full-length and a truncated, were crystallized and the structures were solved at 2.5 and 2.9 Å resolution, respectively. The <scene name='55/559101/Cv/2'>overall structure of AoCO4</scene> is predominantly &#945;-helical. A <span style="color:lime;background-color:black;font-weight:bold;">four-helix bundle forms the core (shown in green)</span> of the protein and the <scene name='55/559101/Cv/3'>catalytic copper site is situated within this helical bundle</scene>. The truncated form lacks the <span style="color:cyan;background-color:black;font-weight:bold;">long N-terminal &#945;-helix (shown in cyan)</span>, which is not part of the <span style="color:lime;background-color:black;font-weight:bold;">central helical bundle</span>. Both the full-length and truncated form exists as a similar transient dimer (surface area 855 Å<sup>2</sup>) in crystal.
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Two different forms of AoCO4, called as a full-length and a truncated, were crystallized and the structures were solved at 2.5 and 2.9 Å resolution, respectively. The <scene name='55/559101/Cv/2'>overall structure of AoCO4</scene> is predominantly &#945;-helical. A <span style="color:lime;background-color:black;font-weight:bold;">four-helix bundle forms the core (shown in green)</span> of the protein and the <scene name='55/559101/Cv/3'>catalytic copper site is situated within this helical bundle</scene>. The truncated form lacks the <span style="color:cyan;background-color:black;font-weight:bold;">long N-terminal &#945;-helix (shown in cyan)</span>, which is not part of the <span style="color:lime;background-color:black;font-weight:bold;">central helical bundle</span>. Carbohydrates are colored in white. Both the full-length and truncated form exists as a similar transient dimer (surface area 855 Å<sup>2</sup>) in crystal.
The crystal structure of AoCO4 demonstrated that mono-oxygenase and diphenolase reactivity cannot be explained by accessibility to copper ions. Based on the observations that CuA is restricted by a Phe residue in plant catechol oxidases, but not in tyrosinases, it has been suggested that o-diphenols bind to CuB, whereas monophenols bind to CuA. However, both copper ions were solvent-exposed and accessible to substrates in AoCO4.
The crystal structure of AoCO4 demonstrated that mono-oxygenase and diphenolase reactivity cannot be explained by accessibility to copper ions. Based on the observations that CuA is restricted by a Phe residue in plant catechol oxidases, but not in tyrosinases, it has been suggested that o-diphenols bind to CuB, whereas monophenols bind to CuA. However, both copper ions were solvent-exposed and accessible to substrates in AoCO4.

Revision as of 12:46, 17 September 2013

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