Membrane-Bound Energy Transducers and their Interactions with Biological membranes
Ion-translocating integral membrane proteins are involved in a wide range of functions in living cells such as signal transduction, energy conversion and nerve conduction. Because many of these proteins share common structural elements and mechanistic properties, a shortcut to understanding their function at the molecular level is to find general concepts to describe them. More specifically, our studies involve the use of a broad range of biochemical and biophysical techniques to investigate the structure and function of membrane proteins involved in electron and proton transport. In addition, we investigate the role of the membrane in providing functional connectivity between membrane-bound proton transporters.
- Von Ballmoos C., Gennis R.B., Ädelroth P. and Brzezinski, P. (2011)
Kinetic design of the respiratory oxidases.
Proc. Natl. Acad. Sci. USA, 108, 11057-11062
- Johansson, A.-L., Högbom, M., Carlsson, J., Gennis, R.B. and Brzezinski P. (2013)
Role of aspartate 132 at the orifice of a proton pathway in cytochrome c oxidase.
Proc. Natl. Acad. Sci. USA 110, 8912-8917.
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Our research is finaced by Vetenskapsrådet, the Knut and Alice Wallenberg Foundation and Wenner-Gren Stiftelsenn
Transport genom cellmembraner
Biologiska membraner utgör gränsytor mellan levande organismer och omgivningen, omger celler och definierar utsträckningen för organeller inne i celler. Transport av stora och små molekyler samt joner över membraner spelar därför en central roll för allt liv. Detta projekt är fokuserat på förståelse av mekanismer för hur elektroner och protoner rör sig genom membraner. Dessa processer är centrala bland annat för kroppens energiomsättning och även mycket små störningar leder till allvarliga sjukdomar.
Structure and Function of Membrane-Bound Energy Transducers
Ion-translocating integral membrane proteins are involved in a wide range of functions in living cells such as signal transduction, energy conversion and nerve conduction. Because many of these proteins share common structural elements and mechanistic properties, a shortcut to understanding their function at the molecular level is to find general concepts to describe them. More specifically, our studies involve the use of a broad range of biochemical and biophysical techniques to investigate the structure and function of membrane proteins involved in electron and proton transport. In addition, we investigate the role of protein-membrane interactions in controlling the protein dynamics and functional properties.
Proton Microcircuits at the Membrane-Water Interface
Proton transport across biological membranes is a key step of the energy-conservation machinery in living organisms. Results from a number of experimental and theoretical studies indicate that the membrane plays an important role in this process. In this project we use fluorescence correlation spectroscopy and time-resolved spectroscopic techniques to study the local protonation dynamics of single pH-sensitive fluorophores conjugated to liposome membranes or to the surfaces of membrane proteins. The hypothesis is that a proton appearing on the membrane surface would be transferred laterally over long distances such that under the non-equilibrium conditions in a living cell the proton concentration at the surface would be higher than that in the bulk solution. Furthermore, when considering proton-uptake reactions, this property of membrane surfaces would act to extend the effective surface area of a proton-collecting array of a membrane-bound transporter. Analogous properties have also been suggested for membrane-bound transport proteins where surface-exposed protonatable groups (Asp, Glu and His) would act as "proton-collecting antennae" extending the proton-collecting area of an intraprotein proton pathway.
Membrane-coated Mesoporous Silica Particles
The aim of this project is to develop a system for functional studies of membrane-bound transporters using membrane-coated mesoporous silica particles (MSP). The advantage of using this system, compared to conventional vesicles is the long-term stability, that the size of the particles allows visualization of transport processes using light microscopy, the possibility to encapsulate various compounds within the particles and a uniform size distribution. Particles.jpg We have incorporated CytcO into the MSP-adsorbed membrane and showed that the enzyme was fully functional, both with respect to catalysis of O2 reduction to water, and charge separation across the membrane (Nordlund et al. 2009). The particle system will be used for real-time visualization of proton transport across the membrane using STED microscopy. Ongoing studies are also aimed at using the membrane-covered MSPs for diagnostic (imaging) and therapeutic (drug delivery) purposes. Here, we encapsulate various compounds (c.f. drugs) within the membrane-covered particles and modify the membrane with peptides/proteins that are targeted towards specific tissues.
Development of a Bacterial Sensor for Landmines
This project is aimed at development of bacterial sensors to detect land mines. The genetic system of the soil bacterium P. putida was modified in such a way that exposure to TNT results in production of the green-fluorescent protein. Thus, the bacteria become fluorescent in the presence of explosive-contaminated soil. The idea is to use the bacteria as biosensors to detect traces of e.g. TNT at mine fields.