Low NO concentration dependence of reductive nitrosylation reaction of hemoglobin. J Biol Chem 2012 May 25;287(22):18262-74
Date
04/12/2012Pubmed ID
22493289Pubmed Central ID
PMC3365727DOI
10.1074/jbc.M111.298927Scopus ID
2-s2.0-84861548242 (requires institutional sign-in at Scopus site) 40 CitationsAbstract
The reductive nitrosylation of ferric (met)hemoglobin is of considerable interest and remains incompletely explained. We have previously observed that at low NO concentrations the reaction with tetrameric hemoglobin occurs with an observed rate constant that is at least 5 times faster than that observed at higher concentrations. This was ascribed to a faster reaction of NO with a methemoglobin-nitrite complex. We now report detailed studies of this reaction of low NO with methemoglobin. Nitric oxide paradoxically reacts with ferric hemoglobin with faster observed rate constants at the lower NO concentration in a manner that is not affected by changes in nitrite concentration, suggesting that it is not a competition between NO and nitrite, as we previously hypothesized. By evaluation of the fast reaction in the presence of allosteric effectors and isolated β- and α-chains of hemoglobin, it appears that NO reacts with a subpopulation of β-subunit ferric hemes whose population is influenced by quaternary state, redox potential, and hemoglobin dimerization. To further characterize the role of nitrite, we developed a system that oxidizes nitrite to nitrate to eliminate nitrite contamination. Removal of nitrite does not alter reaction kinetics, but modulates reaction products, with a decrease in the formation of S-nitrosothiols. These results are consistent with the formation of NO(2)/N(2)O(3) in the presence of nitrite. The observed fast reductive nitrosylation observed at low NO concentrations may function to preserve NO bioactivity via primary oxidation of NO to form nitrite or in the presence of nitrite to form N(2)O(3) and S-nitrosothiols.
Author List
Tejero J, Basu S, Helms C, Hogg N, King SB, Kim-Shapiro DB, Gladwin MTAuthor
Neil Hogg PhD Senior Associate Dean, Professor in the Biophysics department at Medical College of WisconsinMESH terms used to index this publication - Major topics in bold
Allosteric RegulationHemoglobins
Humans
Hydrogen-Ion Concentration
Nitric Oxide
Nitroso Compounds
Oxidation-Reduction
Protein Binding
