PMID- 16060655
OWN - NLM
STAT- MEDLINE
DCOM- 20051221
LR  - 20161019
IS  - 0006-2960 (Print)
IS  - 0006-2960 (Linking)
VI  - 44
IP  - 31
DP  - 2005 Aug 9
TI  - The protonation state of a heme propionate controls electron transfer in 
      cytochrome c oxidase.
PG  - 10466-74
AB  - In cytochrome c oxidase (CcO), exergonic electron transfer reactions from 
      cytochrome c to oxygen drive proton pumping across the membrane. Elucidation of 
      the proton pumping mechanism requires identification of the molecular components 
      involved in the proton transfer reactions and investigation of the coupling 
      between internal electron and proton transfer reactions in CcO. While the 
      proton-input trajectory in CcO is relatively well characterized, the components 
      of the output pathway have not been identified in detail. In this study, we have 
      investigated the pH dependence of electron transfer reactions that are linked to 
      proton translocation in a structural variant of CcO in which Arg481, which 
      interacts with the heme D-ring propionates in a proposed proton output pathway, 
      was replaced with Lys (RK481 CcO). The results show that in RK481 CcO the 
      midpoint potentials of hemes a and a(3) were lowered by approximately 40 and 
      approximately 15 mV, respectively, which stabilizes the reduced state of Cu(A) 
      during reaction of the reduced CcO with O(2). In addition, while the pH 
      dependence of the F --> O rate in wild-type CcO is determined by the protonation 
      state of two protonatable groups with pK(a) values of 6.3 and 9.4, only the 
      high-pK(a) group influences this rate in RK481 CcO. The results indicate that the 
      protonation state of the Arg481 heme a(3) D-ring propionate cluster having a 
      pK(a) of approximately 6.3 modulates the rate of internal electron transfer and 
      may act as an acceptor of pumped protons.
FAU - Branden, Gisela
AU  - Branden G
AD  - Department of Biochemistry and Biophysics, The Arrhenius Laboratories for Natural 
      Sciences, Stockholm University, SE-106 91 Stockholm, Sweden.
FAU - Branden, Magnus
AU  - Branden M
FAU - Schmidt, Bryan
AU  - Schmidt B
FAU - Mills, Denise A
AU  - Mills DA
FAU - Ferguson-Miller, Shelagh
AU  - Ferguson-Miller S
FAU - Brzezinski, Peter
AU  - Brzezinski P
LA  - eng
GR  - R01 GM026916/GM/NIGMS NIH HHS/United States
GR  - GM 20488/GM/NIGMS NIH HHS/United States
GR  - GM 26916/GM/NIGMS NIH HHS/United States
PT  - Journal Article
PT  - Research Support, N.I.H., Extramural
PT  - Research Support, Non-U.S. Gov't
PT  - Research Support, U.S. Gov't, P.H.S.
PL  - United States
TA  - Biochemistry
JT  - Biochemistry
JID - 0370623
RN  - 0 (Propionates)
RN  - 0 (Proton Pumps)
RN  - 0 (Protons)
RN  - 0 (Solutions)
RN  - 18535-39-2 (heme a)
RN  - 42VZT0U6YR (Heme)
RN  - EC 1.9.3.1 (Electron Transport Complex IV)
SB  - IM
MH  - Animals
MH  - Catalytic Domain
MH  - Electron Transport
MH  - Electron Transport Complex IV/*chemistry/*metabolism
MH  - Heme/*analogs & derivatives/chemistry/metabolism
MH  - Horses
MH  - Hydrogen-Ion Concentration
MH  - Models, Chemical
MH  - Oxidation-Reduction
MH  - Photolysis
MH  - Propionates/*chemistry/metabolism
MH  - Proton Pumps/*chemistry/metabolism
MH  - *Protons
MH  - Rhodobacter sphaeroides
MH  - Solutions
MH  - Thermodynamics
EDAT- 2005/08/03 09:00
MHDA- 2005/12/22 09:00
CRDT- 2005/08/03 09:00
PHST- 2005/08/03 09:00 [pubmed]
PHST- 2005/12/22 09:00 [medline]
PHST- 2005/08/03 09:00 [entrez]
AID - 10.1021/bi0502745 [doi]
PST - ppublish
SO  - Biochemistry. 2005 Aug 9;44(31):10466-74. doi: 10.1021/bi0502745.