Osmotically-induced tension and the binding of N-BAR protein to lipid vesicles

• Published in: Soft matter 2016-01, Vol.12 (8), p.2465-2472
• Main Authors: Hutchison, Jaime B, Karunanayake Mudiyanselage, Aruni P. K. K, Weis, Robert M, Dinsmore, Anthony D
• Format: Article
• Language: English
• Subjects: Animals; Binding; Biophysical Phenomena; Constants; Drosophila; Drosophila - chemistry; Drosophila - genetics; Drosophila - metabolism; Drosophila Proteins - chemistry; Drosophila Proteins - metabolism; Kinetics; Lipids; Membranes; Monitors; Nerve Tissue Proteins - chemistry; Nerve Tissue Proteins - genetics; Nerve Tissue Proteins - metabolism; Osmosis; Protein Binding; Protein Domains; Proteins; Stresses; Synaptic Vesicles - chemistry; Synaptic Vesicles - metabolism; Vesicles
• ISSN: 1744-683X; 1744-6848
• DOI: 10.1039/c5sm02496j

The binding affinity of a curvature-sensing protein domain (N-BAR) is measured as a function of applied osmotic stress while the membrane curvature is nearly constant. Varying the osmotic stress allows us to control membrane tension, which provides a probe of the mechanism of binding. We study the N-BAR domain of the Drosophila amphiphysin and monitor its binding on 50 nm-radius vesicles composed of 90 mol% DOPC and 10 mol% PIP. We find that the bound fraction of N-BAR is enhanced by a factor of approximately 6.5 when the tension increases from zero to 2.6 mN m −1 . This tension-induced response can be explained by the hydrophobic insertion mechanism. From the data we extract a hydrophobic domain area that is consistent with known structure. These results indicate that membrane stress and strain could play a major role in the previously reported curvature-affinity of N-BAR. The binding affinity of a curvature-sensing protein domain (N-BAR) is measured as a function of applied osmotic stress while the membrane curvature is nearly constant.