Subunit positioning and transmembrane helix organisation in the core dimerof photosystem II

Recently 3D structural models of the photosystem II (PSII) core dimer compl exes of higher plants (spinach) and cyanobacteria (Synechococcus elongatus) have been derived by electron [Rhee et al. (1998) Nature 396, 283-286; Han kamer et al. (2001) J. Struct. Biol., in press] and X-ray [Zouni et al. (20 01) Nature 409, 739-743] crystallography respectively. The intermediate res olutions of these structures do not allow direct identification of side cha ins and therefore many of the individual subunits within the structure are unassigned. Here we review the structure of the higher plant PSII core dime r and provide evidence for the tentative assignment of the low molecular we ight subunits. In so doing we highlight the similarities and differences be tween the higher plant and cyanobacterial structures. (C) 2001 Federation o f European Biochemical Societies. Published by Elsevier Science B.V. All ri ghts reserved.