FIGURE 7.

Graphic illustrating the possible effects of membrane thinning on LHCII. Compression of the LHC structure in A is achieved by (i) increased tilting of the transmembrane helices, causing structural changes in the Arg-Glu interlocked core (B; the affected core region is encircled) or (ii) reorientation of protein segments close to the water interface, causing structural changes in the regions near the lumenal and stromal sites (C; the affected end regions are encircled). A structural change as depicted in B will affect the orientations of Chl602 and Chl610 (green diamonds) that are ligated to the Arg-Glu interlocked core. However, such a structural rearrangement is unlikely according to the preserved NMR chemical shifts of the Chl-ligating Arg. The structural change depicted in C could reorient the luteins (orange rods) that have their head groups bound to the affected protein end regions.