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. Author manuscript; available in PMC: 2009 Jan 1.
Published in final edited form as: Nat Struct Mol Biol. 2008 Jul;15(7):675–683. doi: 10.1038/nsmb.1455

Figure 1.

Figure 1

Fusion-through hemifusion pathway of lipid bilayer fusion. (a) (i) Pre-fusion contact. (ii) A point-like membrane protrusion minimizes the energy of the hydration repulsion between the proximal leaflets of the membranes coming into immediate contact. (iii) A hemifusion stalk with proximal leaflets fused and distal leaflets unfused. (iv) Stalk expansion yields the hemifusion diaphragm. (v) A fusion pore forms either in the hemifusion diaphragm bilayer or directly from the stalk. Dashed lines show the boundaries of the hydrophobic surfaces of monolayers. (b) Different lipids spontaneously form monolayers of different curvatures and, thus, demonstrate different effective molecular shapes. Monolayers formed by inverted cone–shaped lysophosphatidylcholine (LPC) and by cone-shaped phosphatidylethanolamine (PE) and diacylglycerol (DAG) bulge in the direction of the polar heads and in the direction of the hydrocarbon chains, respectively. Cylindrical phosphatidylcholine (PC) forms an almost flat monolayer.