Fig. 7.
Conformational ensemble proposed for the small, midsized, and large double belts of apoA-IM (top) and apoA-IWT (bottom). The double belts are rotated by ∼180°C with respect to their orientations in Figs. 2–5.Green arrows point to the center of repeat 5. Repeat pair 5/5′, which was proposed to form the lipid presentation tunnel for the LCAT reaction (53), is replaced with 5/9′ pairing in apoA-IM homodimer (green arrows). Arcs indicate constant and variable regions. Gray line in the bottom panels shows swing axis in the apoA-IWT double belt, which connects G65-P66 and G185-G186 hinge regions. These hinges are in registry in the double belt of apoA-IWT (bottom) but in neither in apoA-IM (top) nor in apoA-IP homodimers (supplementary Fig. V), which is expected to impede tetrafoil formation by these homodimers (Fig. 1).