infocus #66 June 2022 Nanoscale imaging of proteins’ filament assembly on membrane in rebuilt cell membrane

Atomic force microscopy (AFM) is a multipurpose technique that can simultaneously produce a high-resolution 3D image while also obtaining mechanical information of samples on surfaces. These abilities make AFM a very useful technique for studying filamentous membrane-bound proteins in their native environment with minimal sample preparation.

Here we report how we used AFM together with other imaging methods to investigate a biomimetic cell membrane. Specifically, we studied how septin proteins, which are part of the cell’s cytoskeleton, bind and polymerise on flat supported lipid bilayers.

With AFM, single filaments and their substructures were visualised which were not resolvable via fluorescence microscopy, while also obtaining height and mechanical stability information. Taken together, this multi-technique study showed that septin form ordered arrays of single and paired filaments on lipid membranes that might mechanically support cells.