ANTENNA PROTEIN-COMPOSITION OF PS-I AND PS-II IN THYLAKOID SUB-DOMAINS

Spinach thylakoids were separated into grana core, grana margin, and t wo different stromal lamella fractions in the absence of detergents. T he levels of all light-harvesting chlorophyll a/b-binding (LHC) protei ns were determined in all fractions, and were normalised to the amount of Photosystem I (PS I) and Photosystem II (PS II) centres. PS I beta in the stroma lamellae was found to have a full complement of Lhca po lypeptides and, probably, one attached LHC II trimer. PS I alpha binds additional LHC II trimers, but PS I centres located in the inner part s of the grana stack lack Lhca1 and are depleted in Lhca4. PS II beta, found in grana margins and stroma lamellae, seems to associate one mo nomer each of Lhcb4, Lhcb5 and Lhcb6 (CP29, CP76 and CP24, respectivel y) and one LHC II trimer consisting of two Lhcb1 and one Lhcb3 subunit . PS II alpha has additional LHC II trimers (consisting of Lhcb1 and L hcb2) attached. We also find evidence for the existence of both PS I a nd PS II centres in the extreme stroma (probably centres being synthes ised or repaired), that lack all LHC proteins. (C) 1997 Published by E lsevier Science B.V.