Figure 6. Tafazzin and lipid packing.

The cartoon shows our current model of how tafazzin acts on mitochondrial membranes. (a) Bilayer-prone PLs form stable arrangements of tightly packed lipid molecules. PL head groups are depicted as circles and fatty acids as color-coded rectangles. Blue and cyan represent saturated residues and yellow represents unsaturated residues. Only one leaflet of the lipid bilayer is shown. (b) Bending of the membrane will disturb the packing order of bilayer PLs, which is thermodynamically unfavorable but may facilitate intermixing with LPLs, a requirement for the tafazzin reaction. (c) In the presence of tafazzin (TAZ), transacylations will reshuffle the acyl residues in order to optimize lipid packing. In this example, diunsaturated PLs (yellow-yellow) are formed because they promote negative curvature due to their shape. We propose that highly curved membranes promote the reaction of tafazzin and tafazzin, in turn, stabilizes curvature.