Abstract
BAR (Bin/Amphiphysin/Rvs) domains and amphipathic
a-helices (AHs) are believed to be sensors of membrane
curvature thus facilitating the assembly of protein complexes
on curved membranes. Here, we used quantitative
fluorescence microscopy to compare the binding of both
motifs on single nanosized liposomes of different diameters
and therefore membrane curvature. Characterization of
members of the three BAR domain families showed surprisingly
that the crescent-shaped BAR dimer with its positively
charged concave face is not able to sense membrane
curvature. Mutagenesis on BAR domains showed that
membrane curvature sensing critically depends on the
N-terminal AH and furthermore that BAR domains sense
membrane curvature through hydrophobic insertion in
lipid packing defects and not through electrostatics.
Consequently, amphipathic motifs, such as AHs, that are
often associated with BAR domains emerge as an important
means for a protein to sense membrane curvature.
Measurements on single liposomes allowed us to document
heterogeneous binding behaviour within the ensemble and
quantify the influence of liposome polydispersity on bulk
membrane curvature sensing experiments. The latter
results suggest that bulk liposome-binding experiments
should be interpreted with great caution.
Keyword: Single liposomes,BAR domain,Amphipathic a-helix,Membrane insertion,Membrane curvature sensing
Keyword: Single liposomes,BAR domain,Amphipathic a-helix,Membrane insertion,Membrane curvature sensing
Original language | English |
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Journal | E M B O Journal |
Volume | 28 |
Pages (from-to) | 3303-3314 |
ISSN | 0261-4189 |
DOIs | |
Publication status | Published - 2009 |
Externally published | Yes |