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Loss of phylloquinone in Chlamydomonas affects plastoquinone pool size and photosystem II synthesis

Lefebvre-Legendre, Linnka
Rappaport, Fabrice
Finazzi, Giovanni
Published in Journal of Biological Chemistry. 2007, vol. 282, no. 18, p. 13250-13263
Abstract Phylloquinone functions as the electron transfer cofactor at the A(1) site of photosystem I. We have isolated and characterized a mutant of Chlamydomonas reinhardtii, menD1, that is deficient in MenD, which encodes 2-succinyl-6-hydroxy-2,4-cyclohexadiene-1-carboxylate synthase, an enzyme that catalyzes the first specific step of the phylloquinone biosynthetic pathway. The mutant is photosynthetically active but light-sensitive. Analysis of total pigments by mass spectrometry reveals that phylloquinone is absent in menD1, but plastoquinone levels are not affected. This is further confirmed by the rescue of menD1 by addition of phylloquinone to the growth medium. Analysis of electron transfer by absorption spectroscopy indicates that plastoquinone replaces phylloquinone in photosystem I and that electron transfer from A(1) to the iron-sulfur centers is slowed down at least 40-fold. Consistent with a replacement of phylloquinone by plastoquinone, the size of the free plastoquinone pool of menD1 is reduced by 20-30%. In contrast to cyanobacterial MenD-deficient mutants, photosystem I accumulates normally in menD1, whereas the level of photosystem II declines. This decrease is because of reduced synthesis of the photosystem II core subunits. The relationship between plastoquinone occupancy of the A(1) site in photosystem I and the reduced accumulation of photosystem II is discussed.
Keywords Algal Proteins/genetics/metabolismAnimalsChlamydomonas reinhardtii/enzymology/geneticsCoenzymes/metabolismElectron Transport/geneticsMutationOxo-Acid-Lyases/genetics/metabolismPhotosystem I Protein Complex/genetics/metabolismPhotosystem II Protein Complex/genetics/metabolismPlastoquinone/metabolismVitamin K 1/metabolism
PMID: 17339322
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Other version: http://www.jbc.org/cgi/reprint/282/18/13250
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LEFEBVRE-LEGENDRE, Linnka et al. Loss of phylloquinone in Chlamydomonas affects plastoquinone pool size and photosystem II synthesis. In: Journal of Biological Chemistry, 2007, vol. 282, n° 18, p. 13250-13263. https://archive-ouverte.unige.ch/unige:2407

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Deposited on : 2009-08-11

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