PMID- 15100045
OWN - NLM
STAT- MEDLINE
DCOM- 20040617
LR  - 20161126
IS  - 0006-3002 (Print)
IS  - 0006-3002 (Linking)
VI  - 1655
IP  - 1-3
DP  - 2004 Apr 12
TI  - Implications of ligand binding studies for the catalytic mechanism of cytochrome 
      c oxidase.
PG  - 298-305
AB  - The reaction of oxidized bovine heart cytochrome c oxidase (CcO) with one 
      equivalent of hydrogen peroxide results in the formation of two spectrally 
      distinct species. The yield of these two forms is controlled by the ionization of 
      a group with a pK(a) of 6.6. At basic pH, where this group is deprotonated, an 
      intermediate called P dominates (P, because it was initially believed to be a 
      peroxy compound). At acidic pH where the group is protonated, a different 
      species, called F (ferryl intermediate) is obtained. We previously proposed that 
      the only difference between these two species is the presence of one proton in 
      the catalytic center of F that is absent in P. It is now suggested that the 
      catalytic center of this F form has the same redox and protonation state as a 
      second ferryl intermediate produced at basic pH by two equivalents of hydrogen 
      peroxide; the role of the second equivalent of H(2)O(2) is that of a proton donor 
      in the conversion of P to F. Two chloride-binding sites have been detected in 
      oxidized CcO. One site is located at the binuclear center; the second site was 
      identified from the sensitivity of g=3 signal of cytochrome a to chloride in the 
      EPR spectra of oxidized CcO. Turnover of CcO releases chloride from the catalytic 
      center into the medium probably by one of the hydrophobic channels, proposed for 
      oxygen access, with an orientation parallel to the membrane plane. Chloride in 
      the binuclear center is most likely not involved in CcO catalysis. The influence 
      of the second chloride site upon several reactions of CcO has been assessed. No 
      correlation was found between chloride binding to the second site and the 
      reactions that were examined.
FAU - Fabian, Marian
AU  - Fabian M
AD  - Department of Biochemistry and Cell Biology, Rice University MS 140, P.O. Box 
      1892, 6100 Main, Houston TX 77005, USA. fabian@bioc.rice.edu
FAU - Skultety, Ludovit
AU  - Skultety L
FAU - Jancura, Daniel
AU  - Jancura D
FAU - Palmer, Graham
AU  - Palmer G
LA  - eng
GR  - GM 55807/GM/NIGMS NIH HHS/United States
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
PT  - Research Support, U.S. Gov't, P.H.S.
PT  - Review
PL  - Netherlands
TA  - Biochim Biophys Acta
JT  - Biochimica et biophysica acta
JID - 0217513
RN  - 0 (Chlorides)
RN  - 0 (Ligands)
RN  - BBX060AN9V (Hydrogen Peroxide)
RN  - EC 1.9.3.1 (Electron Transport Complex IV)
SB  - IM
MH  - Animals
MH  - Binding Sites
MH  - Catalysis
MH  - Cattle
MH  - Chlorides/metabolism
MH  - Electron Spin Resonance Spectroscopy
MH  - Electron Transport Complex IV/*chemistry/*metabolism
MH  - Hydrogen Peroxide/metabolism
MH  - Hydrogen-Ion Concentration
MH  - In Vitro Techniques
MH  - Ligands
MH  - Myocardium/enzymology
RF  - 88
EDAT- 2004/04/22 05:00
MHDA- 2004/06/18 05:00
CRDT- 2004/04/22 05:00
PHST- 2003/04/23 00:00 [received]
PHST- 2003/07/17 00:00 [accepted]
PHST- 2004/04/22 05:00 [pubmed]
PHST- 2004/06/18 05:00 [medline]
PHST- 2004/04/22 05:00 [entrez]
AID - S0005272803002196 [pii]
AID - 10.1016/j.bbabio.2003.07.008 [doi]
PST - ppublish
SO  - Biochim Biophys Acta. 2004 Apr 12;1655(1-3):298-305. doi: 
      10.1016/j.bbabio.2003.07.008.