Unprecedented Fe(IV) Species in a Diheme Protein MauG: A Quantum Chemical Investigation on the Unusual Mossbauer Spectroscopic Properties

Ferryl species are important catalytic intermediates in heme enzymes. A recent experimental investigation of a diheme protein MauG reported the first case of using two Fe(IV) species as an alternative to compound I in catalysis. Both Fe(IV) species have unusual Mossbauer properties, which was found to originate from novel structural features based on a quantum chemical investigation. With comparison with the previously reported Fe-IV=O and Fe-IV-OH species, results here provide evidence of new mechanisms by which proteins influence the properties of ferryl species by directly providing the O via Tyr or stabilizing exogenous O via hydrogen bonding interaction. These results expand our ability to identify and evaluate high-valent heme proteins and models.