Membrane-bending proteins (pink) quickly aggregate and vesiculate a membrane (blue/yellow) in silico.

DESERNO/MACMILLAN

Membrane-bending proteins can attract each other when the curves they create overlap, according to a computer simulation by Benedict Reynwar, Markus Deserno, and colleagues (Max Planck Institute, Mainz, Germany).

The energy required for membrane reshaping—as needed for endocytosis, vesiculation, etc.—is too great for one membrane-bending protein alone to achieve, so cooperation is essential. How cooperation occurs, however, has been a bit of a mystery.

Part of the mystery stems from previous theoretical calculations that predicted that curves induced by a membrane-bending protein repel other proteins of its kind. Experimental systems, on the other hand, suggested that membrane curving might be enough to aggregate the responsible proteins. Ruling out other specific protein–protein interactions is difficult, however.

Now, in silico simulations by Reynwar et al. show that, as suggested by experimentation, curves can be enough to pull together membrane benders. The team created computerized proteins that induced a membrane curve geometry similar to that of a real membrane-bending protein called BAR domain. In a simulated lipid bilayer in which the proteins freely diffused, the induced deformed regions encircling the proteins soon overlapped. The proteins did not then diffuse away but instead aggregated such that the area of deformation grew, eventually leading to vesiculation.

The ease with which the simulated proteins aggregated and promoted vesiculation—within just milliseconds—suggests that real cells must keep a tight leash on their benders.

Reference:

Reynwar, B.J., et al.
2007
.
Nature.
447
:
461
–464.