Dataset Information

Measuring the energetics of membrane protein dimerization in mammalian membranes.

ABSTRACT: Thus far, quantitative studies of lateral protein interactions in membranes have been restricted peptides or simplified protein constructs in lipid vesicles or bacterial membranes. Here we show how free energies of membrane protein dimerization can be measured in mammalian plasma membrane-derived vesicles. The measurements, performed in single vesicles, utilize the quantitative imaging FRET (QI-FRET) method. The experiments are described in a step-by-step protocol. The protein characterized is the transmembrane domain of glycophorin A, the most extensively studied membrane protein, known to form homodimers in hydrophobic environments. The results suggest that molecular crowding in cellular membranes has a dramatic effect on the strength of membrane protein interactions.

SUBMITTER: Chen L

PROVIDER: S-EPMC3860826 | biostudies-literature | 2010 Mar

REPOSITORIES: biostudies-literature

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Measuring the energetics of membrane protein dimerization in mammalian membranes.

Chen Lirong L Novicky Lawrence L Merzlyakov Mikhail M Hristov Tihomir T Hristova Kalina K

Journal of the American Chemical Society 20100301 10

Thus far, quantitative studies of lateral protein interactions in membranes have been restricted peptides or simplified protein constructs in lipid vesicles or bacterial membranes. Here we show how free energies of membrane protein dimerization can be measured in mammalian plasma membrane-derived vesicles. The measurements, performed in single vesicles, utilize the quantitative imaging FRET (QI-FRET) method. The experiments are described in a step-by-step protocol. The protein characterized is t ...[more]

PMID: 20158179

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Project description:Membrane proteins are essential in the exchange processes of cells. In spite of great breakthrough in soluble proteins studies, membrane proteins structures, functions and interactions are still a challenge because of the difficulties related to their hydrophobic properties. Most of the experiments are performed with detergent-solubilized membrane proteins. However widely used micellar systems are far from the biological two-dimensions membrane. The development of new biomimetic membrane systems is fundamental to tackle this issue.We present an original approach that combines the Fluorescence Recovery After fringe Pattern Photobleaching technique and the use of a versatile sponge phase that makes it possible to extract crucial informations about interactions between membrane proteins embedded in the bilayers of a sponge phase. The clear advantage lies in the ability to adjust at will the spacing between two adjacent bilayers. When the membranes are far apart, the only possible interactions occur laterally between proteins embedded within the same bilayer, whereas when membranes get closer to each other, interactions between proteins embedded in facing membranes may occur as well.After validating our approach on the streptavidin-biotinylated peptide complex, we study the interactions between two membrane proteins, MexA and OprM, from a Pseudomonas aeruginosa efflux pump. The mode of interaction, the size of the protein complex and its potential stoichiometry are determined. In particular, we demonstrate that: MexA is effectively embedded in the bilayer; MexA and OprM do not interact laterally but can form a complex if they are embedded in opposite bilayers; the population of bound proteins is at its maximum for bilayers separated by a distance of about 200 A, which is the periplasmic thickness of Pseudomonas aeruginosa. We also show that the MexA-OprM association is enhanced when the position and orientation of the protein is restricted by the bilayers. We extract a stoichiometry for the complex that exhibits a strong pH dependance: from 2 to 6 MexA per OprM trimer when the pH decreases from 7.5 to 5.5.Our technique allows to study membrane protein associations in a membrane environment. It provides some challenging information about complexes such as geometry and stoichiometry.

Dataset Information

Measuring the energetics of membrane protein dimerization in mammalian membranes.

Publications

Measuring the energetics of membrane protein dimerization in mammalian membranes.

Similar Datasets

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