Molecular mechanisms for generating transmembrane proton gradients

M. R. Gunner*, Muhamed Amin, Xuyu Zhu, Jianxun Lu

*Bijbehorende auteur voor dit werk

Onderzoeksoutput: Review articlepeer review

26 Citaten (Scopus)
14 Downloads (Pure)

Samenvatting

Membrane proteins use the energy of light or high energy substrates to build a transmembrane proton gradient through a series of reactions leading to proton release into the lower pH compartment (P-side) and proton uptake from the higher pH compartment (N-side). This review considers how the proton affinity of the substrates, cofactors and amino acids are modified in four proteins to drive proton transfers. Bacterial reaction centers (RCs) and photosystem II (PSII) carry out redox chemistry with the species to be oxidized on the P-side while reduction occurs on the N-side of the membrane. Terminal redox cofactors are used which have pK(a)s that are strongly dependent on their redox state, so that protons are lost on oxidation and gained on reduction. Bacteriorhodopsin is a true proton pump. Light activation triggers trans to cis isomerization of a bound retinal. Strong electrostatic interactions within clusters of amino acids are modified by the conformational changes initiated by retinal motion leading to changes in proton affinity, driving transmembrane proton transfer. Cytochrome c oxidase (CcO) catalyzes the reduction of O-2 to water. The protons needed for chemistry are bound from the N-side. The reduction chemistry also drives proton pumping from N- to P-side. Overall, in CcO the uptake of 4 electrons to reduce O-2 transports 8 charges across the membrane, with each reduction fully coupled to removal of two protons from the N-side, the delivery of one for chemistry and transport of the other to the P-side. (C) 2013 Elsevier B.V. All rights reserved.

Originele taal-2English
Pagina's (van-tot)892-913
Aantal pagina's22
TijdschriftBiochimica et Biophysica Acta
Volume1827
Nummer van het tijdschrift8-9
DOI's
StatusPublished - 2013
Extern gepubliceerdJa

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