Membrane-bending mechanism of amphiphysin N-BAR domains.

BAR domains are highly conserved protein domains participating in a diversity of cellular processes that involve membrane remodeling. The mechanisms underlying such remodeling are debated. For the relatively well-studied case of amphiphysin N-BAR domain, one suggested mechanism involves scaffolding, i.e., binding of a negatively charged membrane to the protein's positively charged curved surface. An alternative mechanism suggests that insertion of the protein's N-terminal amphipathic segments (N-helices H0) into the membrane leads to bending. Here, we address the issue through all-atom and coarse-grained simulations of multiple amphiphysin N-BAR domains and their components interacting with a membrane. We observe that complete N-BAR domains and BAR domains without H0s bend the membrane, but H0s alone do not, which suggests that scaffolding, rather than helix insertion, plays a key role in membrane sculpting by amphiphysin N-BAR domains.