title: The extrinsic proteins of photosystem II in photosynthetic organisms: distribution, properties and evolutionary implications.
abstract: Photosystem II from higher plant chloroplasts contains extrinsic proteins of molecular weights 33, 23 and 16 kDa. Cyanobacteria, which are thought to be closely related to the evolutionary progenitor of chloroplasts, have a protein homologous to the largest of these, but lack homologues of the smaller ones. Here we report immunological evidence for the occurrence of the 33 kDa extrinsic protein in red and chromophyte algae and its absence from anoxygenic photosynthetic bacteria. The 23 kDa protein was absent from all three groups. The red algal protein was found to be hydrophilic and rather more loosely associated with the thylakoid membrane than its higher plant equivalent. These findings support an origin for all plastids among the oxygenic prokaryotes, in contrast to the phylogeny inferred from ribulose bisphosphate carboxylase-oxygenase sequence data.
authors: Department of Biochemistry, University of Cambridge, U.K.
authors: M S
authors: MS
authors: Fairweather
authors: J C
authors: JC
authors: Packer
authors: C J
authors: CJ
authors: Howe
mesh_terms: D005075:Biological Evolution; D000458:Cyanobacteria / Q000378:metabolism; D056890:Eukaryota / Q000145:classification / Q000378:metabolism*; D008970:Molecular Weight; D000459:Phaeophyceae / Q000378:metabolism; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry / Q000378:metabolism*; D045332:Photosystem II Protein Complex; D018087:Plastids / Q000378:metabolism; D000461:Rhodophyta / Q000378:metabolism; D013559:Symbiosis
chemical_list: D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex