For cells to function properly1, membrane proteins must be able to diffuse within biological membranes. The functions of these membrane proteins depend on their position and also on protein–protein and protein–lipid interactions2. However, so far, it has not been possible to study simultaneously the structure and dynamics of biological membranes. Here, we show that the motion of unlabelled membrane proteins can be characterized using high-speed atomic force microscopy3. We find that the molecules of outer membrane protein F (OmpF) are widely distributed in the membrane as a result of diffusion-limited aggregation, and while the overall protein motion scales roughly with the local density of proteins in the membrane, individual protein molecules can also diffuse freely or become trapped by protein–protein interactions. Using these measurements, and the results of molecular dynamics simulations, we determine an interaction potential map and an interaction pathway for a membrane protein, which should provide new insights into the connection between the structures of individual proteins and the structures and dynamics of supramolecular membranes.
At a glance
- Membranes are more mosaic than fluid. Nature 438, 578–580 (2005).
- Emerging roles for lipids in shaping membrane–protein function. Nature 459, 379–385 (2009). , , &
- A high-speed atomic force microscope for studying biological macromolecules. Proc. Natl Acad. Sci. USA 98, 12468–12472 (2001). et al.
- Imaging of single molecule diffusion. Proc. Natl Acad. Sci. USA 93, 2926–2929 (1996). , , , &
- Characterization of the major envelope protein from Escherichia coli. J. Biol. Chem. 249, 8019–8029 (1974).
- Porin channel triplets merge into single outlets in Escherichia coli outer membranes. Nature 317, 643–645 (1985). , , , &
- New major outer membrane proteins found in an Escherichia coli tolF mutant resistant to bacteriophage TuIb. J. Bacteriol. 133, 1478–1483 (1978). &
- Cell entry mechanism of enzymatic bacterial colicins: porin recruitment and the thermodynamics of receptor binding. Proc. Natl Acad. Sci. USA 102, 13849–13854 (2005). , , , &
- Crystal structures of the OmpF porin: function in a colicin translocon. EMBO J. 27, 2171–2180 (2008). , , , &
- Software for drift compensation, particle tracking and particle analysis of high-speed atomic force microscopy image series. J. Mol. Recognit. 25, 292–298 (2012). , , , &
- Fractal methods and results in cellular morphology—dimensions, lacunarity and multifractals. J. Neurosci. Methods 69, 123–136 (1996). , &
- Diffusion-limited aggregation, a kinetic critical phenomenon. Phys. Rev. Lett. 47, 1400–1403 (1981). &
- Mobility of BtuB and OmpF in the Escherichia coli outer membrane: implications for dynamic formation of a translocon complex. Biophys. J. 99, 3880–3886 (2010). et al.
- Confined lateral diffusion of membrane receptors as studied by single particle tracking (nanovid microscopy). Effects of calcium-induced differentiation in cultured epithelial cells. Biophys. J. 65, 2021–2040 (1993). , &
- Macromolecule diffusion and confinement in prokaryotic cells. Curr. Opin. Biotechnol. 22, 117–126 (2011). &
- Voronoi and Voronoi-related tessellations in studies of protein structure and interaction. Curr. Opin. Struct. Biol. 14, 233–241 (2004).
- Crystal structures explain functional properties of two E. coli porins. Nature 358, 727–733 (1992). et al.
- The orientation of porin OmpF in the outer membrane of Escherichia coli. J. Mol. Biol. 233, 400–413 (1993). , , &
- Dynamic multiple-target tracing to probe spatiotemporal cartography of cell membranes. Nature Methods 5, 687–694 (2008). , , &
- Dynamics in the plasma membrane: how to combine fluidity and order. EMBO J. 25, 3446–3457 (2006). , , &
- Amplitude Modulation Atomic Force Microscopy 77–90 (Wiley, 2010). (ed.) in
- High-speed atomic force microscopy reveals rotary catalysis of rotorless F1-ATPase. Science 333, 755–758 (2011). , , &
- Proteins of the outer-membrane of gram-negative bacteria. Annu. Rev. Microbiol. 34, 369–422 (1980). &
- Molecular simulations of lipid-mediated protein–protein interactions. Biophys. J. 95, 1851–1865 (2008). , &
- Crowding effects on diffusion in solutions and cells. Annu. Rev. Biophys. 37, 247–263 (2008). &
- Brownian motion in biological membranes. Proc. Natl Acad. Sci. USA 72, 3111–3113 (1975). &
- Paradigm shift of the plasma membrane concept from the two-dimensional continuum fluid to the partitioned fluid: high-speed single-molecule tracking of membrane molecules. Annu. Rev. Biophys. Biomol. Struct. 34, 351–378 (2005). et al.
- Structural basis for sugar translocation through maltoporin channels at 3.1 Å resolution. Science 267, 512–514 (1995). , , &
- Kinetics of bimolecular reactions in model bilayers and biological membranes. A critical review. Biophys. Chem. 123, 77–94 (2006). &
- Lateral mobility of proteins in liquid membranes revisited. Proc. Natl Acad. Sci. USA 103, 2098–2102 (2006). et al.
- Supplementary information (8.78 MB)
- Supplementary Movie 1 (6.57 MB)
Supplementary Movie 1
- Supplementary Movie 2 (712 KB)
Supplementary Movie 2
- Supplementary Movie 3 (1.10 MB)
Supplementary Movie 3
- Supplementary Movie 4 (8.60 MB)
Supplementary Movie 4
- Supplementary Movie 5 (976 KB)
Supplementary Movie 5
- Supplementary Movie 6 (280 KB)
Supplementary Movie 6
- Supplementary Movie 7 (288 KB)
Supplementary Movie 7
- Supplementary Movie 8 (124 KB)
Supplementary Movie 8
- Supplementary Movie 9 (11.7 MB)
Supplementary Movie 9
- Supplementary Movie 10 (8.08 MB)
Supplementary Movie 10