PMID- 9920871
OWN - NLM
STAT- MEDLINE
DCOM- 19990226
LR  - 20210209
IS  - 0021-9258 (Print)
IS  - 0021-9258 (Linking)
VI  - 274
IP  - 6
DP  - 1999 Feb 5
TI  - An electron spin resonance spin-trapping investigation of the free radicals 
      formed by the reaction of mitochondrial cytochrome c oxidase with H2O2.
PG  - 3308-14
AB  - The reaction of purified bovine mitochondrial cytochrome c oxidase (CcO) and 
      hydrogen peroxide was studied using the ESR spin-trapping technique. A 
      protein-centered radical adduct was trapped by 5, 5-dimethyl-1-pyrroline N-oxide 
      and was assigned to a thiyl radical adduct based on its hyperfine coupling 
      constants of aN = 14.7 G and abetaH = 15.7 G. The ESR spectra obtained using the 
      nitroso spin traps 3,5-dibromo-4-nitrosobenzenesulfonic acid (DBNBS) and 
      2-methyl-2-nitrosopropane (MNP) indicated that both DBNBS/.CcO and MNP/.CcO 
      radical adducts are immobilized nitroxides formed by the trapping of 
      protein-derived radicals. Alkylation of the free thiols on the enzyme with 
      N-ethylmaleimide (NEM) prevented 5, 5-dimethyl-1-pyrroline N-oxide adduct 
      formation and changed the spectra of the MNP and DBNBS radical adducts. 
      Nonspecific protease treatment of MNP-d9/.NEM-CcO converted its spectrum from 
      that of an immobilized nitroxide to an isotropic three-line spectrum 
      characteristic of rapid molecular motion. Super-hyperfine couplings were detected 
      in this spectrum and assigned to the MNP/.tyrosyl adduct(s). The inhibition of 
      either CcO or NEM-CcO with potassium cyanide prevented detectable MNP adduct 
      formation, indicating heme involvement in the reaction. The results indicate that 
      one or more cysteine residues are the preferred reductant of the presumed ferryl 
      porphyrin cation radical residue intermediate. When the cysteine residues are 
      blocked with NEM, one or more tyrosine residues become the preferred reductant, 
      forming the tyrosyl radical.
FAU - Chen, Y R
AU  - Chen YR
AD  - Laboratory of Pharmacology and Chemistry, NIEHS, National Institutes of Health, 
      Research Triangle Park, North Carolina 27709, USA. chen6@niehs.nih.gov
FAU - Gunther, M R
AU  - Gunther MR
FAU - Mason, R P
AU  - Mason RP
LA  - eng
PT  - Journal Article
PL  - United States
TA  - J Biol Chem
JT  - The Journal of biological chemistry
JID - 2985121R
RN  - 0 (Benzenesulfonates)
RN  - 0 (Free Radicals)
RN  - 0 (Nitroso Compounds)
RN  - 0 (Spin Labels)
RN  - 83016-63-1 (3,5-dibromo-4-nitrosobenzenesulfonate)
RN  - BBX060AN9V (Hydrogen Peroxide)
RN  - EC 1.9.3.1 (Electron Transport Complex IV)
RN  - JGX6N17V2U (tert-nitrosobutane)
SB  - IM
MH  - Animals
MH  - Benzenesulfonates
MH  - Cattle
MH  - Electron Spin Resonance Spectroscopy
MH  - Electron Transport Complex IV/*metabolism
MH  - Free Radicals
MH  - Hydrogen Peroxide/*metabolism
MH  - Mitochondria, Heart/*enzymology
MH  - Nitroso Compounds
MH  - Spin Labels
EDAT- 1999/01/28 00:00
MHDA- 1999/01/28 00:01
CRDT- 1999/01/28 00:00
PHST- 1999/01/28 00:00 [pubmed]
PHST- 1999/01/28 00:01 [medline]
PHST- 1999/01/28 00:00 [entrez]
AID - S0021-9258(19)87948-6 [pii]
AID - 10.1074/jbc.274.6.3308 [doi]
PST - ppublish
SO  - J Biol Chem. 1999 Feb 5;274(6):3308-14. doi: 10.1074/jbc.274.6.3308.