TY  - JOUR
AU  - Mulkidjanian, A. Y.
AU  - Heberle, J.
AU  - Cherepanov, D. A.
TI  - Protons @ interfaces: implications for biological energy conversion
JO  - Biochimica et biophysica acta / Bioenergetics
VL  - 1757
SN  - 0005-2728
CY  - Amsterdam
PB  - Elsevier
M1  - PreJuSER-57132
SP  - 913 - 930
PY  - 2006
N1  - Record converted from VDB: 12.11.2012
AB  - The review focuses on the anisotropy of proton transfer at the surface of biological membranes. We consider (i) the data from "pulsed" experiments, where light-triggered enzymes capture or eject protons at the membrane surface, (ii) the electrostatic properties of water at charged interfaces, and (iii) the specific structural attributes of proton-translocating enzymes. The pulsed experiments revealed that proton exchange between the membrane surface and the bulk aqueous phase takes as much as about 1 ms, but could be accelerated by added mobile pH-buffers. Since the accelerating capacity of the latter decreased with the increase in their electric charge, it was concluded that the membrane surface is separated from the bulk aqueous phase by a barrier of electrostatic nature. The barrier could arise owing to the water polarization at the negatively charged membrane surface. The barrier height depends linearly on the charge of penetrating ions; for protons, it has been estimated as about 0.12 eV. While the proton exchange between the surface and the bulk aqueous phase is retarded by the interfacial barrier, the proton diffusion along the membrane, between neighboring enzymes, takes only microseconds. The proton spreading over the membrane is facilitated by the hydrogen-bonded networks at the surface. The membrane-buried layers of these networks can eventually serve as a storage/buffer for protons (proton sponges). As the proton equilibration between the surface and the bulk aqueous phase is slower than the lateral proton diffusion between the "sources" and "sinks", the proton activity at the membrane surface, as sensed by the energy transducing enzymes at steady state, might deviate from that measured in the adjoining water phase. This trait should increase the driving force for ATP synthesis, especially in the case of alkaliphilic bacteria.
KW  - Biological Transport
KW  - Cations: chemistry
KW  - Electron Transport Complex IV: chemistry
KW  - Energy Metabolism
KW  - Kinetics
KW  - Membranes: physiology
KW  - Models, Biological
KW  - Models, Molecular
KW  - Protein Conformation
KW  - Protons
KW  - Water: chemistry
KW  - Cations (NLM Chemicals)
KW  - Protons (NLM Chemicals)
KW  - Water (NLM Chemicals)
KW  - Electron Transport Complex IV (NLM Chemicals)
KW  - J (WoSType)
LB  - PUB:(DE-HGF)16
C6  - pmid:16624250
UR  - <Go to ISI:>//WOS:000241481300005
DO  - DOI:10.1016/j.bbabio.2006.02.015
UR  - https://juser.fz-juelich.de/record/57132
ER  -