PMID- 21344856
OWN - NLM
STAT- MEDLINE
DCOM- 20110804
LR  - 20211020
IS  - 1520-4995 (Electronic)
IS  - 0006-2960 (Print)
IS  - 0006-2960 (Linking)
VI  - 50
IP  - 14
DP  - 2011 Apr 12
TI  - Alternative initial proton acceptors for the D pathway of Rhodobacter sphaeroides 
      cytochrome c oxidase.
PG  - 2820-8
LID - 10.1021/bi102002v [doi]
AB  - To characterize protein structures that control proton uptake, we assayed forms 
      of cytochrome c oxidase (CcO) containing a carboxyl or a thiol group in line with 
      the initial, internal waters of the D pathway for proton transfer in the presence 
      and absence of subunit III. Subunit III provides approximately half of the 
      protein surrounding the entry region of the D pathway. The N139D/D132N mutant 
      contains a carboxyl group 6 A within the D pathway and lacks the normal, 
      surface-exposed proton acceptor, Asp-132. With subunit III, the steady-state 
      activity of this mutant is slow, but once subunit III is removed, its activity is 
      the same as that of wild-type CcO lacking subunit III ( approximately 1800 H+/s). Thus, a 
      carboxyl group approximately 25% within the pathway enhances proton uptake even though the 
      carboxyl has no direct contact with bulk solvent. Protons from solvent apparently 
      move to internal Asp-139 through a short file of waters, normally blocked by 
      subunit III. Cys-139 also supports rapid steady-state proton uptake, 
      demonstrating that an anion other than a carboxyl can attract and transfer 
      protons into the D pathway. When both Asp-132 and Asp/Cys-139 are present, the 
      removal of subunit III increases CcO activity to rates greater than that of 
      normal CcO because of simultaneous proton uptake by two initial acceptors. The 
      results show how the environment of the initial proton acceptor for the D pathway 
      in these CcO forms dictates the pH range of CcO activity, with implications for 
      the function of Asp-132, the normal proton acceptor.
FAU - Varanasi, Lakshman
AU  - Varanasi L
AD  - Department of Biochemistry, University of Mississippi Medical Center, Jackson, 
      Mississippi 39216, United States.
FAU - Hosler, Jonathan
AU  - Hosler J
LA  - eng
GR  - R01 GM056824/GM/NIGMS NIH HHS/United States
GR  - R01 GM056824-09/GM/NIGMS NIH HHS/United States
GR  - GM56824/GM/NIGMS NIH HHS/United States
PT  - Journal Article
PT  - Research Support, N.I.H., Extramural
DEP - 20110321
PL  - United States
TA  - Biochemistry
JT  - Biochemistry
JID - 0370623
RN  - 0 (Bacterial Proteins)
RN  - 0 (Protein Subunits)
RN  - 0 (Protons)
RN  - 30KYC7MIAI (Aspartic Acid)
RN  - EC 1.9.3.1 (Electron Transport Complex IV)
SB  - IM
MH  - Aspartic Acid/chemistry/genetics/metabolism
MH  - Bacterial Proteins/*chemistry/genetics/metabolism
MH  - Binding Sites/genetics
MH  - Biocatalysis
MH  - Electron Transport Complex IV/*chemistry/genetics/metabolism
MH  - Hydrogen-Ion Concentration
MH  - Models, Molecular
MH  - Mutation
MH  - Protein Subunits/chemistry/genetics/metabolism
MH  - *Protons
MH  - Rhodobacter sphaeroides/*enzymology/genetics
PMC - PMC3082432
MID - NIHMS277650
EDAT- 2011/02/25 06:00
MHDA- 2011/08/05 06:00
PMCR- 2012/04/12
CRDT- 2011/02/25 06:00
PHST- 2011/02/25 06:00 [entrez]
PHST- 2011/02/25 06:00 [pubmed]
PHST- 2011/08/05 06:00 [medline]
PHST- 2012/04/12 00:00 [pmc-release]
AID - 10.1021/bi102002v [doi]
PST - ppublish
SO  - Biochemistry. 2011 Apr 12;50(14):2820-8. doi: 10.1021/bi102002v. Epub 2011 Mar 
      21.