title: The secondary electron acceptor of photosystem I in Gloeobacter violaceus PCC 7421 is menaquinone-4 that is synthesized by a unique but unknown pathway.
abstract: The secondary electron acceptor of photosystem (PS) I in the cyanobacterium Gloeobacter violaceus PCC 7421 was identified as menaquinone-4 (MQ-4) by comparing high performance liquid chromatograms and absorption spectra with an authentic compound. The MQ-4 content was estimated to be two molecules per one molecule of chlorophyll (Chl) a', a constituent of P700. Comparative genomic analyses showed that six of eight men genes, encoding phylloquinone/MQ biosynthetic enzymes, are missing from the G. violaceus genome. Since G. violaceus clearly synthesizes MQ-4, the combined results indicate that this cyanobacterium must have a novel pathway for the synthesis of 1,4-dihydroxy-2-naphthoic acid.
authors.affiliation: Department of Technology and Ecology, Hall of Global Environmental Research, Kyoto University, Kyoto 606-8501, Japan. mamo-mi@mm1.mbox.media.kyoto-u.ac.jp
authors.forename: Mamoru
authors.initials: M
authors.lastname: Mimuro
authors.forename: Tohru
authors.initials: T
authors.lastname: Tsuchiya
authors.forename: Hidetoshi
authors.initials: H
authors.lastname: Inoue
authors.forename: Yumiko
authors.initials: Y
authors.lastname: Sakuragi
authors.forename: Yuka
authors.initials: Y
authors.lastname: Itoh
authors.forename: Takanori
authors.initials: T
authors.lastname: Gotoh
authors.forename: Hideaki
authors.initials: H
authors.lastname: Miyashita
authors.forename: Donald A
authors.initials: DA
authors.lastname: Bryant
authors.forename: Masami
authors.initials: M
authors.lastname: Kobayashi
mesh_terms: D002734:Chlorophyll / Q000031:analogs & derivatives / Q000032:analysis; D000458:Cyanobacteria / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016680:Genome, Bacterial; D009284:Naphthols / Q000378:metabolism; D045331:Photosystem I Protein Complex / Q000235:genetics / Q000378:metabolism*; D010837:Vitamin K 1 / Q000032:analysis / Q000378:metabolism; D024482:Vitamin K 2 / Q000031:analogs & derivatives* / Q000032:analysis / Q000378:metabolism
chemical_list: D009284:Naphthols; D045331:Photosystem I Protein Complex; D024482:Vitamin K 2; D002734:Chlorophyll; C024023:1,4-dihydroxy-2-naphthoic acid; C085815:chlorophyll a'; C030814:menatetrenone; D010837:Vitamin K 1