ArfGAP1 generates an Arf1 gradient on continuous lipid membranes displaying flat and curved regions |
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Authors: | Patricia Bassereau Bruno Goud Jean‐Baptiste Manneville Bruno Antonny |
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Affiliation: | 1. Laboratoire Membranes and Cellular Functions, Institut Curie, CNRS UMR 168, Paris, France;2. Laboratoire Mécanismes moléculaires du transport intracellulaire, Institut Curie, CNRS UMR 144, Paris, France;3. Institut de Pharmacologie Moléculaire et Cellulaire, Université de Nice Sophia Antipolis et CNRS, Valbonne, France |
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Abstract: | ArfGAP1, which promotes GTP hydrolysis on the small G protein Arf1 on Golgi membranes, interacts preferentially with positively curved membranes through its amphipathic lipid packing sensor (ALPS) motifs. This should influence the distribution of Arf1‐GTP when flat and curved regions coexist on a continuous membrane, notably during COPI vesicle budding. To test this, we pulled tubes from giant vesicles using molecular motors or optical tweezers. Arf1‐GTP distributed on the giant vesicles and on the tubes, whereas ArfGAP1 bound exclusively to the tubes. Decreasing the tube radius revealed a threshold of R≈35 nm for the binding of ArfGAP1 ALPS motifs. Mixing catalytic amounts of ArfGAP1 with Arf1‐GTP induced a smooth Arf1 gradient along the tube. This reflects that Arf1 molecules leaving the tube on GTP hydrolysis are replaced by new Arf1‐GTP molecules diffusing from the giant vesicle. The characteristic length of the gradient is two orders of magnitude larger than a COPI bud, suggesting that Arf1‐GTP diffusion can readily compensate for the localized loss of Arf1 during budding and contribute to the stability of the coat until fission. |
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Keywords: | ALPS motif diffusion membrane curvature membrane tube optical tweezers |
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