Photosystem antenna proteins

In addition to the antenna proteins, photosystem I is associated with at least 9 non-pigmented proteins with apparent molecular weights ranging from 4 to 22 kD (15-17). Six of these are shown in Figure 2, and they are all extrinsic, based on hydropathy plots, and extractibility. Subunit II is involved in binding ferredoxin, and subunit IV (which may be confused with subunit III because the two can exchange positions in SDS-PAGE) is probably located on the lumen side, where it binds plastocyanin. Subunit VII, which is coded by chloroplast DNA, contains the electron transport acceptors and F (16). Functions for the other subunits remain to be elucidated. 

Phycobilins 500 Covalently bound to proteins on the outer surface of photosynthetic membranes in cyanobacteria and red algae serve in light-harvesting antennae of Photosystem II... 

Zhang H, Goodman HM and Jansson S (1997) Antisense inhibition of the Photosystem I antenna protein Lhca4 in Arabidopsis thaliana. Plant Physiol 115 1525-1531... 

Kiss, A., Crouchman, S., Ruban, A.V., and Horton, P. 2008. The PsbS protein controls the organisation of the photosystem II antenna in higher plant thylakoid membranes. J. Biol. Chem., 283 3972-3978. 

Fig. 3 Schematic model of light-harvesting compartments in photosynthetic organisms and their position with respect to the membrane and the reaction centers. RC1(2) Photosystem I(II) reaction centre. Peripheral membrane antennas Chlorosome/FMO in green sulfur and nonsulfur bacteria, phycobilisome (PBS) in cyanobacteria and rhodophytes and peridinin-chlorophyll proteins (PCP) in dyno-phytes. Integral membrane accessory antennas LH2 in purple bacteria, LHC family in all eukaryotes. Integral membrane core antennas B808-867 complex in green nonsulfur bacteria, LH1 in purple bacteria, CP43/CP47 (not shown) in cyanobacteria and all eukaryotes.

The present paper summarises our recent results relating to the location and structure of the reaction centres of photosystems I and II, with particular reference to the organisation of the chlorophyll-proteins and the transfer of excitation energy from antennae to the reaction centres. 

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