A fundamental question about how cell membranes can get dents in them was answered by Vinzenz Unger of Yale University School of Medicine and his colleagues.
They found that proteins containing a region called an F-BAR domain form scaffolds in the peripheral cytoplasm and bring about invaginations in the cell membrane. Unger's team recreated the interactions between membranes and F-BAR proteins in a test tube, and then observed the results using electron microscopy.
F-BAR proteins, which have an elongated crescent shape, are exceptionally rigid and interact with membranes through their charged surfaces, according to the study. The proteins assemble into helical lattices and form clusters on membranes; the lattices can then bend the membranes to adopt the F-BAR protein's curved shape.