Adding material to one leaflet of the lipid bilayer, at the expense of the other, can do work and bend the membrane. The findings of Chen et al. (page 1223) are the first hint that such a mechanism may be used in protein trafficking, in this case in the budding yeast TGN. Doubts remain, however, about the ability of Drs2p (the trafficking protein studied by Chen et al.) to move lipids from one side of a membrane to the other.
Chen et al. identify a drs2 mutation as being synthetically lethal with a deletion in ADP-ribosylation factor 1 (ARF1). ARF1 is one of two redundant ARFs. Both recruit two coat proteins: COPI for Golgi to ER transport, and clathrin, possibly for TGN to endosome transport. Drs2p appears to function in the clathrin pathway, as a drs2 deletion interacts only...