Cytochrome bci Metal Cofactor Specifics

TABLE 7.6 Metal Cofactor Distances in cytochrome bci [2Fe-2S] Position and Mobility 

PDB No. (reference, date) Species (Crystal Space Group, resolution. A) Inhibitor or Substrate (PDB abbreviation, binding site) heme Ci— [2Fe-2S] (Fei and/or Fe,) (A) [2Fe-2S] (Fei and/or Fe2)—heme be (A) heme Ol— heme bn (A) [2Fe-2S]. Position and Mobility  

Both the N- and C-termini are located in the matrix. The two hemes are bound within the four helix bundle of helices A-B-C-D. The iron ion in heme Bl carries axial his83 (helix B, Fe-Ne2 = 2.08 A) and hisl82 (helix D, Fe-Ne2 = 

06 A) ligands, while the iron ion in heme bn carries his97 (helix B, Fe-Ne2 = 

07 A) and hisl96 (heUx D, Fe-Ne2 = 2.05 A). These histidines are invariant in sequences of cytochrome b as well as in cytochrome be as described for cytochrome b(6)f above. 

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