The X-ray crystal structure of Shewanella oneidensis OmcA reveals new insight at the microbe-mineral interface.

The X-ray crystal structure of Shewanella oneidensis OmcA, an extracellular decaheme cytochrome involved in mineral reduction, was solved to a resolution of 2.7 Å. The four OmcA molecules in the asymmetric unit are arranged so the minimum distance between heme 5 on adjacent OmcA monomers is 9 Å, indicative of a transient OmcA dimer capable of intermolecular electron transfer. A previously identified hematite binding motif was identified near heme 10, forming a hydroxylated surface that would bring a heme 10 electron egress site to ∼10 Å of a mineral surface.