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Functional interactions between membrane-bound transporters and membranes
Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
2010 (English)In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 107, no 36, 15763-15767 p.Article in journal (Refereed) Published
Abstract [en]

One key role of many cellular membranes is to hold a transmembrane electrochemical ion gradient that stores free energy, which is used, for example, to generate ATP or to drive transmembrane transport processes. In mitochondria and many bacteria, the gradient is maintained by proton-transport proteins that are part of the respiratory (electron-transport) chain. Even though our understanding of the structure and function of these proteins has increased significantly, very little is known about the specific role of functional protein-membrane and membrane-mediated protein-protein interactions. Here, we have investigated the effect of membrane incorporation on proton-transfer reactions within the membrane-bound proton pump cytochrome c oxidase. The results show that the membrane acts to accelerate proton transfer into the enzyme's catalytic site and indicate that the intramolecular proton pathway is wired via specific amino acid residues to the two-dimensional space defined by the membrane surface. We conclude that the membrane not only acts as a passive barrier insulating the interior of the cell from the exterior solution, but also as a component of the energy-conversion machinery.

Place, publisher, year, edition, pages
2010. Vol. 107, no 36, 15763-15767 p.
Keyword [en]
cytochrome aa(3), electron transfer, energy transduction, membrane protein, respiration
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:su:diva-50181DOI: 10.1073/pnas.1006109107ISI: 000281637800027OAI: oai:DiVA.org:su-50181DiVA: diva2:381909
Note
authorCount :4Available from: 2010-12-29 Created: 2010-12-21 Last updated: 2017-12-11Bibliographically approved
In thesis
1. Membrane effects on proton transfer in cytochrome c oxidase
Open this publication in new window or tab >>Membrane effects on proton transfer in cytochrome c oxidase
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The biological membrane is composed of lipids and proteins that make up dynamic barriers around cells and organelles. Membrane-spanning proteins are involved in many key processes in the cell such as energy conversion, nerve conduction and signal transduction. These proteins interact closely with lipids as well as with other proteins in the membrane, which modulates and affects their structure and function. In the energy-conversion process, membrane-bound proton-transport proteins maintain an electrochemical proton gradient across the mitochondrial inner membrane or the cytoplasmic membrane of bacteria. This gradient is utilized for ATP synthesis or transport of ions and molecules across the membrane. Results from earlier studies have shown that proton transporters are influenced by their environment.

Here, one of these proton transporters, cytochrome c oxidase, has been purified and reconstituted into liposomes or nanodiscs and membrane effects on specific proton-transfer processes were studied. In these studies we observed that the membrane accelerated proton transfer to the surface of cytochrome c oxidase and that there is a protonic link, via a Glu residue that mediates proton transfer from the membrane surface to a proton-transfer pathway in this protein. In addition, the membrane was shown to modulate specific internal electron and proton-transfer reactions.

The results from these studies show that the membrane composition influences transmembrane transport. Consequently, our understanding of these processes requires investigation of these transporter proteins in different membrane-mimetic systems of variable and well-defined composition. Furthermore, the data show that membrane surfaces facilitate lateral proton transfer which is presumably essential for maintaining high efficiency in energy conversion. This is particular important in organisms such as alkaliphilic bacteria where the driving force of the electrochemical proton gradient, between the bulk solution on each side of the membrane is not sufficient for ATP synthesis.

Place, publisher, year, edition, pages
Department of Biochemistry and Biophysics, Stockholm University, 2012. 57 p.
Keyword
cytochrom c oxidase, lipids, membrane, proton transfer
National Category
Biochemistry and Molecular Biology
Research subject
Biochemistry
Identifiers
urn:nbn:se:su:diva-75633 (URN)978-91-7447-482-4 (ISBN)
Public defence
2012-06-15, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 10:00 (English)
Opponent
Supervisors
Available from: 2012-05-11 Created: 2012-04-24 Last updated: 2012-05-15Bibliographically approved

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Näsvik Öjemyr, LindaLee, Hyun JuBrzezinski, Peter
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