Tryptophan-mediated charge-resonance stabilization in the bis -Fe(IV) redox state of MauG

• DOI: 10.1073/pnas.1301544110
• Publication Date: 2013-05-30T05:03:13Z
• Authors: Jiafeng Geng; Kednerlin Dornevil; Victor L. Davidson; Aimin Liu
• Keywords: Paracoccus denitrificans

The diheme enzyme MauG catalyzes posttranslational modifications of a methylamine dehydrogenase precursor protein to generate tryptophan tryptophylquinone cofactor. MauG-catalyzed reaction proceeds via bis -Fe(IV) intermediate in which one heme is present as Fe(IV)=O and the other Fe(IV) with axial histidine tyrosine ligation. Herein, unique near-infrared absorption feature exhibited specifically described, evidence presented that it results from charge-resonance-transition phenomenon. As two hemes are physically separated by 14.5 Å, hole-hopping mechanism proposed residue located between reversibly oxidized reduced increase effective electronic coupling element enhance rate reversible electron transfer MauG. Analysis structure reveals this rapid enough enable charge-resonance stabilization state without direct contact hemes. finding phenomenon explains why stabilized does not permanently oxidize its own aromatic residues.