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Abstract

Endophilin A1, a cytoplasmic protein essential for the budding and fission of synaptic vesicles from presynaptic plasma membranes, is implicated in the generation of membrane curvature. Endophilin A1 exhibits intrinsic lysophosphaticlic acid acyl transferase activity, reflecting its interaction with both the hydrophobic portion and the headgroup of acidic phospholipids. A recent study demonstrates that enclophilin A1 binds to liposomes and alone is sufficient to deform them into narrow tubules, thus generating positive bilayer curvature. The recently identified endophilins B, which associate with membranes of the early secretory pathway, also bind to acidic phospholipids and tubulate liposomes, as do the endophilin- interacting proteins amphiphysin and dynamin. Thus, a novel concept for tubulo-vesicular membrane dynamics emerges in which a team of proteins distinct from, but often operating in concert with, the 'classical' coat proteins is pivotal in the generation of membrane curvature.