Asp‐193 and Glu‐218 of subunit II are involved in the Mn2+‐binding of Paracoccus denitrificans cytochrome c oxidase

Abstract
Cytochrome c oxidase contains a binding site for a non‐redox‐active metal at the interface of subunits I and II, usually a magnesium ion. In Paracoccus denitrificans oxidase, typically 20% may be replaced by manganese, using standard growth media. Site‐directed mutants were constructed in subunit II (D193N and E218Q), and the isolated enzymes analyzed by total‐reflection X‐ray fluorescence spectrometry and EPR. Both mutants show a strong reduction of the manganese stoichiometry and a diminished electron transfer activity, demonstrating that D193 and E218 are involved in the binding of a manganese/magnesium ion in this site.