Crystal structure of the multicopper oxidase from the pathogenic bacterium Campylobacter jejuni CGUG11284: characterization of a metallo-oxidase

Multicopper oxidases are a multi-domain family of enzymes that are able to couple oxidation of substrates with reduction of dioxygen to water. These enzymes are capable of oxidizing a vast range of substrates, varying from aromatic to inorganic compounds such as metals. This metallo-oxidase activity observed in several members of this family has been linked to mechanisms of homeostasis in different organisms. Recently, a periplasmic multicopper oxidase, encoded by Campylobacter jejuni, has been characterised and associated with copper homeostasis and with the protection against oxidative stress as it may scavenge metallic ions into their less toxic form and also inhibit the formation of radical oxygen species. In order to contribute to the understanding of its functional role, the crystal structure of the recombinant McoC (Campylobacter jejuni CGUG11284) has been determined at 1.95 ? resolution and its structural and biochemical characterizations undertaken. The results obtained indicate that McoC has the characteristic fold of a laccase having, besides the catalytic centres, another putative binding site for metals. Indeed, its biochemical and enzymatic characterization shows that McoC is essentially a metallo-oxidase, showing low enzymatic efficiency towards phenolic substrates.