Nitrite binding to globins: linkage isomerism, EPR silence and reductive chemistry.
Bottom Line: We have used EPR (electron paramagnetic resonance) and DFT (density functional theory) to explore these binding modes to myoglobin and hemoglobin.The EPR and DFT data show that both nitrite linkage isomers can be present at the same time and that the two isomers are readily interconvertible in solution.The millisecond-scale process of nitrite reduction by Hb is investigated in search of the elusive Fe(II)-nitrite adduct.
Affiliation: "Babeş-Bolyai" University, 1 Mihail Kogalniceanu str., RO-400084 Cluj-Napoca, Romania; Department of Biological Sciences, University of Essex, Wivenhoe Park, Colchester, Essex CO4 3SQ, UK. Electronic address: firstname.lastname@example.org.Show MeSH
Mentions: Fig. 5 illustrates the reactions that may occur upon the treatment of ferric or ferrous hemoglobin with nitrite in the presence of a reducing agent. Ferric hemoglobin binds reversibly to the nitrite generating a complex that may undergo reduction in the presence of a reductive agent forming a ferrous hemoglobin – nitrite complex which, in our knowledge, is yet to be characterized – beyond a report concerning a UV-vis spectrum recorded on a crystal subjected to X-rays in reference . This ferrous–nitrite complex may then, in a proton-dependent process, release a water molecule and form a ferric-NO adduct. The metHb-NO complex can be further reduced to Fe(II)-NO, react with nitric oxide and generate deoxyHb and N2O3, or liberate NO to form metHb. Rifkind and co-workers have described in some detail reactions occurring on longer time scales, of the order of minutes, where ferrous-nitrosyl adducts are indeed eventually detected, with proposed modulation by cysteine 93 [42–45]. They have additionally postulated, based on quasi-steady-state data, that non-negligible amounts of ferrous-nitrite adduct are formed in their experiments.
Affiliation: "Babeş-Bolyai" University, 1 Mihail Kogalniceanu str., RO-400084 Cluj-Napoca, Romania; Department of Biological Sciences, University of Essex, Wivenhoe Park, Colchester, Essex CO4 3SQ, UK. Electronic address: email@example.com.