Proteins in membranes attract each other. A new paper by Afshin Vahid and Timon Idema, that was published in Physical Review Letters, offers a mathematical explanation for this biological phenomenon.

This Friday, 23 September, the paper Pointlike Inclusion Interactions in Tubular Membranes will be published in Physical Review Letters. Vahid and Idema studied the pattern formation of proteins on biological membranes. Such membranes are ubiquitous in the cell, and form the boundary of both the cell itself and its various organelles (the ‘organs’ of the cell).

Biological membranes contain a large number of protein inclusions which are essential for a range of cellular processes. For the proper execution of these processes, the right proteins need to be brought together. One way proteins aggregate is similar to the process by which two bowling balls put on a mattress will roll towards each other, because both of them locally indent the mattress. Similarly, proteins exert forces on each other by deforming the membrane.

Proteins attract
Previous research has shown that identical proteins on a flat membrane always repel. However, in a living cell such membranes are generally not flat but cylindrical. “We have considered the protein-protein forces on a strongly curved, cylindrical membrane, as found in many places inside the living cell”, Idema explains. “From our analytical model, we discovered that identical proteins attract each other along the bent direction of the membrane.” Consequently, multiple such proteins can spontaneously form rings around a tubular membrane.

An application of this result is the process of cellular division, in which such a protein ring is formed at the boundary of the two new cells. The ring then contracts, thereby neatly splitting the membrane of the mother cell into two closed parts for the daughter cells.

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