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. Author manuscript; available in PMC: 2017 Oct 18.
Published in final edited form as: Biochemistry. 2016 Oct 7;55(41):5818–5831. doi: 10.1021/acs.biochem.6b00834

Figure 9.

Figure 9

Diiron core differences between CmlA and sMMOH upon redox change. Active site models adapted from crystallographic data from refs5, 40, 65, 66. Top row: diferrous Fe centers. Bottom row: diferric Fe centers. Left: Fe•••Fe distance contracts while maintaining ∠Fe-O-Fe in sMMOH. Right: ∠Fe-O-Fe increases while maintaining Fe•••Fe distance in CmlA. Distances from EXAFS data from refs19, 58, 67. ∠Fe-O-Fe in italics; calculated by assuming a symmetric diiron core, where d(Fe1-O) = d(Fe2-O). Residues shown in red are proposed to shift during the respective catalytic cycles. Both enzymes have μ-1,1-carboxylato residues in the diferrous state (sMMOH E243 and CmlA D403), but only sMMOH E243 is proposed to shift. Some ligands are omitted for clarity.