title: The antenna system of photosystem II from Thermosynechococcus elongatus at 3.2 A resolution.
abstract: The content and type of cofactors harboured in the Photosystem II core complex (PS IIcc) of the cyanobacterium Thermosynechococcus elongatus has been determined by biochemical and spectroscopic methods. 17 +/- 1 chlorophyll a per pheophytin a and 0.25 beta-carotene per chlorophyll a have been found in re-dissolved crystals of dimeric PS IIcc. The X-ray crystal structure of PS IIcc from Thermosynechococcus elongatus at 3.2 A resolution clearly shows chlorophyll a molecules arranged in two layers close to the cytoplasmic and lumenal sides of the thylakoid membrane. Each of the cytoplasmic layers contains 9 chlorophyll a, whose positions and orientations are related by a local twofold rotation pseudo-C2 axis passing through the non-haem Fe2+. These chlorophyll a are arranged comparably to those in the antenna domains of PsaA and PsaB of cyanobacterial Photosystem I affirming an evolutionary relation. The chlorophyll a in the lumenal layer are less well conserved between Photosystems I and II and even between CP43 and CP47 with 4 chlorophyll a in the former and 7 in the latter.
authors.affiliation: Institute of Chemistry/Crystallography, Free University Berlin, Takustr. 6, 14195 Berlin, Germany.
authors.forename: Bernhard
authors.initials: B
authors.lastname: Loll
authors.forename: Jan
authors.initials: J
authors.lastname: Kern
authors.forename: Athina
authors.initials: A
authors.lastname: Zouni
authors.forename: Wolfram
authors.initials: W
authors.lastname: Saenger
authors.forename: Jacek
authors.initials: J
authors.lastname: Biesiadka
authors.forename: Klaus-Dieter
authors.initials: KD
authors.lastname: Irrgang
mesh_terms: D002851:Chromatography, High Pressure Liquid; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D045332:Photosystem II Protein Complex / Q000737:chemistry* / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism; D046940:Synechococcus / Q000737:chemistry*; D013696:Temperature
chemical_list: D045332:Photosystem II Protein Complex; D021122:Protein Subunits