heme-o and formic-acid

Oxidised, formate-bound and fluoride-bound forms of E. coli cytochrome bo give rise to an electronic absorption band near 630 nm, diagnostic of high-spin ferric haem o, whose position is sensitive to the nature of the bound anion. In all three forms, haem o remains spin-coupled to Cu(B)(II), resulting in distinct broad X-band EPR signals. Those of formate-bound cytochrome bo are similar to the signals seen in slow cytochrome aa3 but cannot be induced by incubation at acid pH suggesting that the endogenous carboxylate believed to be important in slow cytochrome aa3 is not present in cytochrome bo. The oxidised form gives rise to novel EPR signals at g = 3.74 and g = 3.08 which have not been detected in cytochrome aa3 and may arise from a weak magnetic coupling between high-spin haem o, S = 5/2, and Cu(B)(II), S = 1/2.

Topics: Binding Sites; Copper; Cytochrome b Group; Cytochromes; Electron Spin Resonance Spectroscopy; Electron Transport Complex IV; Escherichia coli; Escherichia coli Proteins; Formates; Heme; Oxidation-Reduction; Sodium Fluoride; Spectrophotometry