To determine the physiologically relevant oligomeric form of membrane proteins is extremely challenging. Now an elegant method of counting the oligomers in membrane proteins in near-native states is presented, using photobleaching and nanodiscs formed directly from cellular membranes.

Nearly a third of all proteins within a cell are associated with membranes. These proteins perform diverse functions as receptors, transporters, ion channels and enzymes. Many of these membrane proteins are produced as monomers that oligomerize in specific stoichiometries to form the functional unit. For example, the tetramerization of potassium (K⁺) channels governs every facet of their biology, from ion conduction to tuning their responsiveness. And although the oligomerization of soluble proteins can be studied by several methods, both at single-molecule resolution and in bulk, analysing the oligomerization of membrane proteins is particularly challenging.