Structural Refinement of BAR-PH Domains Remodeling Cell Membrane Using MDFF

Abstract

Membrane remodeling processes participate various cellular activities such as endocytosis, exocytosis, and cell motility. BAR family proteins play important roles in membrane remodeling, however their molecular mechanisms are not fully understood yet. Two mechanisms have been identified previously, scaffolding and helical insertion. Recently we found that BAR-PH domain proteins bind to membrane asymmetrically [Developmental Cell, 31:73 (2014)] for the first time, different for conventional BAR family proteins. In order to further explore its molecular mechanism, in this work, we applied molecular dynamics flexible fitting combined with cryo-electron microscopy data to identify key residues among BAR-PH domains which form helical lattice on membrane tubes with different diameters, 43nm (class 1) and 50nm (class 2), for instance. Comparing resides found in class 1 and class 2 tubes, there are common key residues and unique resides. Furthermore, in vivo and in vitro mutagenesis experiments verify simulation predictions. With mutations, the binding ability of BAR-PH domains to membrane does not change much, while tabulation ratio significantly drops. This work reveals the importance of cooperative binding of BAR-PH domains and the flexibility of BAR-PH cooperative binding in order to control the diameter of tubes.