PMID- 15100047
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  - FTIR studies of internal proton transfer reactions linked to inter-heme electron 
      transfer in bovine cytochrome c oxidase.
PG  - 321-31
AB  - FTIR difference spectroscopy is used to reveal changes in the internal structure 
      and amino acid protonation states of bovine cytochrome c oxidase (CcO) that occur 
      upon photolysis of the CO adduct of the two-electron reduced (mixed valence, MV) 
      and four-electron reduced (fully reduced, FR) forms of the enzyme. FTIR 
      difference spectra were obtained in D(2)O (pH 6-9.3) between the MV-CO adduct 
      (heme a(3) and Cu(B) reduced; heme a and Cu(A) oxidized) and a photostationary 
      state in which the MV-CO enzyme is photodissociated under constant illumination. 
      In the photostationary state, part of the enzyme population has heme a(3) 
      oxidized and heme a reduced. In MV-CO, the frequency of the stretch mode of CO 
      bound to ferrous heme a(3) decreases from 1965.3 cm(-1) at pH* </=7 to 1963.7 
      cm(-1) at pH* 9.3. In the CO adduct of the fully reduced enzyme (FR-CO), the CO 
      stretching frequency is observed at 1963.46+/-0.05 cm(-1), independent of pH. 
      This indicates that in MV-CO there is a group proximal to heme a that 
      deprotonates with a pK(a) of about 8.3, but that remains protonated over the 
      entire pH* range 6-9.3 in FR-CO. The pK(a) of this group is therefore strongly 
      coupled to the redox state of heme a. Following photodissociation of CO from heme 
      a(3) in MV oxidases, the extent of electron transfer from heme a(3) to heme a 
      shows a pH-dependent phase between pH 7 and 9, and a pH-independent phase at all 
      pH's. The FTIR difference spectrum resulting from photolysis of MV-CO exhibits 
      vibrational features of the protein backbone and side chains associated with (1) 
      the loss of CO by the a(3) heme in the absence of electron transfer, (2) the 
      pH-independent phase of the electron transfer, and (3) the pH-dependent phase of 
      the electron transfer. Many infrared features change intensity or frequency 
      during both electron transfer phases and thus appear as positive or negative 
      features in the difference spectra. In particular, a negative band at 1735 cm(-1) 
      and a positive band at 1412 cm(-1) are consistent with the deprotonation of the 
      acidic residue E242. Positive features at 1552 and 1661 cm(-1) are due to amide 
      backbone modes. Other positive and negative features between 1600 and 1700 cm(-1) 
      are consistent with redox-induced shifts in heme formyl vibrations, and the 
      redox-linked protonation of an arginine residue, accompanying electron transfer 
      from heme a(3) to heme a. An arginine could be the residue responsible for the 
      pH-dependent shift in the carbonyl frequency of MV-CO. Specific possibilities as 
      to the functional significance of these observations are discussed.
FAU - McMahon, Benjamin H
AU  - McMahon BH
AD  - Chemistry Division, Bioscience Division, and Center for Nonlinear Studies, Los 
      Alamos National Laboratory, Michelson Res., Bioscience Division, Los Alamos, NM 
      87545, USA.
FAU - Fabian, Marian
AU  - Fabian M
FAU - Tomson, Farol
AU  - Tomson F
FAU - Causgrove, Timothy P
AU  - Causgrove TP
FAU - Bailey, James A
AU  - Bailey JA
FAU - Rein, Francisca N
AU  - Rein FN
FAU - Dyer, R Brian
AU  - Dyer RB
FAU - Palmer, Graham
AU  - Palmer G
FAU - Gennis, Robert B
AU  - Gennis RB
FAU - Woodruff, William H
AU  - Woodruff WH
LA  - eng
GR  - P01 GM068036/GM/NIGMS NIH HHS/United States
GR  - DK36263/DK/NIDDK NIH HHS/United States
GR  - GM 55807/GM/NIGMS NIH HHS/United States
GR  - HL 16101/HL/NHLBI 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  - 42VZT0U6YR (Heme)
RN  - EC 1.9.3.1 (Electron Transport Complex IV)
SB  - IM
MH  - Animals
MH  - Cattle
MH  - Electron Transport
MH  - Electron Transport Complex IV/*chemistry/*metabolism
MH  - Heme/chemistry
MH  - In Vitro Techniques
MH  - Oxidation-Reduction
MH  - Proton-Motive Force
MH  - Spectroscopy, Fourier Transform Infrared
RF  - 71
EDAT- 2004/04/22 05:00
MHDA- 2004/06/18 05:00
CRDT- 2004/04/22 05:00
PHST- 2003/07/04 00:00 [received]
PHST- 2004/01/29 00:00 [revised]
PHST- 2004/01/29 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 - S0005272804000374 [pii]
AID - 10.1016/j.bbabio.2004.01.007 [doi]
PST - ppublish
SO  - Biochim Biophys Acta. 2004 Apr 12;1655(1-3):321-31. doi: 
      10.1016/j.bbabio.2004.01.007.