title: Minor but key chlorophylls in photosystem II.
abstract: A 'metal-free' chlorophyll (Chl) a, pheophytin (Phe) a, functions as the primary electron acceptor in PS II. On the basis of Phe a/PS II = 2, Phe a content is postulated as an index for estimation of the stoichiometry of pigments and photosystems. We found Phe a in a Chl d-dominant cyanobacterium Acaryochloris marina, whereas Phe d was absent. The minimum Chl a:Phe a ratio was 2:2, indicating that the primary electron donor is Chl a, accessory is Chl d, and the primary electron acceptor is Phe a in PS II of A. marina. Chl d was artificially formed by the treatment of Chl a with papain in aqueous organic solvents. Further, we will raise a key question on the mechanisms of water oxidation in PS II.
authors.affiliation: Institute of Materials Science, University of Tsukuba, Tsukuba 305-8573, Japan. masami@ims.tsukuba.ac.jp
authors.forename: Masami
authors.initials: M
authors.lastname: Kobayashi
authors.forename: Satoru
authors.initials: S
authors.lastname: Watanabe
authors.forename: Takanori
authors.initials: T
authors.lastname: Gotoh
authors.forename: Hajime
authors.initials: H
authors.lastname: Koizumi
authors.forename: Yuka
authors.initials: Y
authors.lastname: Itoh
authors.forename: Machiko
authors.initials: M
authors.lastname: Akiyama
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Shiraiwa
authors.forename: Tohru
authors.initials: T
authors.lastname: Tsuchiya
authors.forename: Hideaki
authors.initials: H
authors.lastname: Miyashita
authors.forename: Mamoru
authors.initials: M
authors.lastname: Mimuro
authors.forename: Takashi
authors.initials: T
authors.lastname: Yamashita
authors.forename: Tadashi
authors.initials: T
authors.lastname: Watanabe
mesh_terms: D002734:Chlorophyll / Q000737:chemistry* / Q000378:metabolism; D000077194:Chlorophyll A; D004579:Electron Transport; D004735:Energy Transfer; D056890:Eukaryota / Q000737:chemistry / Q000378:metabolism; D015394:Molecular Structure; D028528:Petroselinum / Q000737:chemistry / Q000378:metabolism; D010674:Pheophytins / Q000737:chemistry* / Q000378:metabolism; D045332:Photosystem II Protein Complex / Q000737:chemistry* / Q000378:metabolism
chemical_list: D010674:Pheophytins; D045332:Photosystem II Protein Complex; D002734:Chlorophyll; C061694:pheophytin a; C107509:chlorophyll d; D000077194:Chlorophyll A