The structure of a ferrous heme-nitro species in the binuclear heme a₃/Cu_B center of ba₃-cytochrome c oxidase as determined by resonance Raman spectroscopy

Abstract

Members of the cytochrome c oxidase family exhibit nitrite reductase activity. In this work, we have characterized a ferrous heme a3-nitro species in ba3-oxidase by resonance Raman spectroscopy. This provides the first evidence for the structure of a nitrite-bound species in the binuclear heme/copper center of cytochrome c oxidases.

Probing the nitrite and nitric oxide reductase activity of cbb3 oxidase: resonance Raman detection of a six-coordinate ferrous heme–nitrosyl species in the binuclear b3/CuB center

“…The species was characterized by the ν(Fe-NO 2 ) and δ(NO 2 ) modes at 568 cm -1 and 786 cm -1 , respectively. 10 Although the 555 cm -1 mode we observe in the cbb 3 /NO 2 reaction appears at a frequency close to that of the ν(Fe-NO 2 ) of the ferrous heme-nitro adduct of ba 3 oxidase, it is also within the range of frequencies reported for ferrous heme-nitrosyl adducts. Indicatively, the ν(Fe-NO) for the six-coordinate ferrous heme-nitrosyl complexes of ba 3 ) and especially to its V68N mutant (551/1595 cm -1 ).…”

“…10 Such difference in the reactivity towards a substrate would not be unprecedented since, as described previously, the bacterial (ba 3 , caa 3 , bo 3 ) oxidases are able to catalyze the reduction of NO to N 2 O in contrast to their mammalian counterpart. [6][7][8] Noteworthy, the molecular mechanism of NO to N 2 O reduction by HCO is also not clarified yet, as diverse species have been observed in the reactions of NO with different members of the HCO family.…”

“…To investigate the reaction of nitrite with cbb 3 oxidase we have used cysteine, which is a mild reductant, instead of other widely used reductants such as dithionite and ascorbate to avoid the non-enzymatic reduction of NO 2 -, as described in previous work. 10 Figure 1 shows the high frequency RR spectra of the reaction of cysteine-reduced cbb 3 In previous work, we reported the first RR detection of a ferrous heme-nitro species in the binuclear heme/copper center of HCO in the ba 3 oxidase/NO 2 reaction. The species was characterized by the ν(Fe-NO 2 ) and δ(NO 2 ) modes at 568 cm -1 and 786 cm -1 , respectively.…”

Nitrogen Oxide Atom-Transfer Redox Chemistry; Mechanism of NO(g) to Nitrite Conversion Utilizing μ-oxo Heme-FeIII–O–CuII(L) Constructs

“…As mentioned in the discussion, strong credence is given to our conclusion about the structure of the mono-NO adduct; such a N-bound nitrite to iron(II) structure was just recently detected for the ba 3 -C c O 33 . This is the first description of a nitrite ion binding to this enzyme center, where the importance of this finding relates to the C c O nitrite reductase function.…”

ns-μs Time-Resolved Step-Scan FTIR of ba3 Oxidoreductase from Thermus thermophilus: Protonic Connectivity of w941-w946-w927

“…Based on the crystal structure cytochrome ba 3 from Thermus thermophilus contains a homodinuclear copper center (Cu A ), a low-spin heme b , and a heme a 3 -Cu B center [2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24]. Cytochrome ba 3 catalyzes the reductions of oxygen (O 2 ) to water (H 2 O) and of nitric oxide (NO) to nitrous oxide (N 2 O), as well and the oxidation of carbon monoxide (CO) to carbon dioxide (CO 2 ) [2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24]. The photolyzed ba 3 -CO species is an excellent model for time-resolved spectroscopic studies [7,8,9,13,15,18,24].…”