title: The nature of the photosystem II reaction centre in the chlorophyll d-containing prokaryote, Acaryochloris marina.
abstract: Pigment-protein complexes enriched in photosystem II (PS II) have been isolated from the chlorophyll (Chl) d containing cyanobacterium, Acaryochloris marina. A small PS II-enriched particle, we call 'crude reaction centre', contained 20 Chl d, 0.5 Chl a and 1 redox active cytochrome b-559 per 2 pheophytin a, plus the D1 and D2 proteins. A larger PS II-enriched particle, we call 'core', additionally bound the antenna complexes, CP47 and CP43, and had a higher chlorophyll per pheophytin ratio. Pheophytin a could be photoreduced in the presence of a strong reductant, indicating that it is the primary electron acceptor in photosystem II of A. marina. A substoichiometric amount of Chl a (less than one chlorophyll a per 2 pheophytin a) strongly suggests that Chl a does not have an essential role in the photochemistry of PS II in this organism. We conclude that PS II, in A. marina, utilizes Chl d and not Chl a as primary electron donor and that the primary electron acceptor is one of two molecules of pheophytin a.
authors.affiliation: School of Biological Sciences, University of Sydney, NSW 2006, Australia.
authors.forename: Min
authors.initials: M
authors.lastname: Chen
authors.forename: Alison
authors.initials: A
authors.lastname: Telfer
authors.forename: Su
authors.initials: S
authors.lastname: Lin
authors.forename: Andrew
authors.initials: A
authors.lastname: Pascal
authors.forename: Anthony W D
authors.initials: AW
authors.lastname: Larkum
authors.forename: James
authors.initials: J
authors.lastname: Barber
authors.forename: Robert E
authors.initials: RE
authors.lastname: Blankenship
mesh_terms: D002734:Chlorophyll / Q000737:chemistry / Q000378:metabolism*; D000458:Cyanobacteria / Q000737:chemistry / Q000378:metabolism*; D045303:Cytochromes b / Q000737:chemistry / Q000378:metabolism; D010084:Oxidation-Reduction; D010674:Pheophytins / Q000737:chemistry / Q000378:metabolism; D010777:Photochemistry; D045332:Photosystem II Protein Complex / Q000378:metabolism*; D011485:Protein Binding; D013057:Spectrum Analysis; D013696:Temperature
chemical_list: D010674:Pheophytins; D045332:Photosystem II Protein Complex; D002734:Chlorophyll; C061694:pheophytin a; C107509:chlorophyll d; D045303:Cytochromes b