Proteins are bio-macromolecules that come in many shapes and forms. They can be viewed as molecular machines and are key players in metabolic processes, intracellular signaling and trafficking, cell-to-cell and long-range communication, among others. Proteins are synthesized as strings of amino acids that then need to fold into a three-dimensional structure to be functional. These structures are not static and one single protein, in many cases, can adopt different conformations, with different activities.

Membrane proteins, such as ion channels, transporters, or receptors, are embedded into cellular membranes where they establish a physical connection between both sides of the membrane. Like this, they take on central roles during intra-cellular signaling as well as cell-to-cell communication. Inserting these proteins into hydrophobic membranes comes with unique challenges and in cells specialized machineries have evolved for this task. We are facing very similar challenges when working with membrane proteins in the lab.

In cells, proteins often form complexes with other proteins or ligands which can lead to the generation of large, multi-molecular signaling complexes. In this scenario, the function of individual proteins can be modulated by specific protein-protein interactions adding an extra level of complexity to protein physiology. It also allows to connect different cellular pathways via shared, participating proteins. We are just in the early stages of understanding the range of functions that can be achieved that way.