Membrane Dynamics: Lipid–Protein Interactions Studied by AFM

The eukaryotic cell has developed distinct membrane compart-

ments, such as the nucleus, mitochondria, lysosomes, Golgi com-

plex, and endoplasmic reticulum (ER). Protein sorting to specific

membrane compartments ensures the correct functions of the

organelles and is accomplished by the proteins’ own targeting

signals (e.g., signals for delivery to the ER, mitochondria, and

chloroplast membranes) acting in concert with an intracellular

vesicle transport system (e.g., from the ER to the Golgi apparatus,

to the lysosome, and to the plasma membrane). The ER is regarded

as an entry point to the vesicle transport system. Newly synthesized

membrane proteins are first inserted into the ER membrane and

then transported to other organelles by a process that involves

vesicle budding from the donor membrane and fusion with the

target membrane. Both proteins and lipids are transported between

organelles in vesicles. AFM can be used to analyze these dynamic

biological processes.