Acridones: A chemically new group of protonophores

G. Horváth, M. Droppa, L. Fodorpataki, A. Istókovics, G. Garab, W. Oettmeier

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

Although the interaction of proton-conducting ionophores (protonophores) with photosynthetic electron transport has been extensively studied during the past decade, the mode of action of protonophores remained uncertain. For a better understanding of the molecular mechanism of the action of protonophores, the introduction of chemically new types of molecules will be required. In this work, we demonstrate that acridones (9-azaanthracene-10- ones) completely fulfill this requirement. At low concentrations of acridones, the thermoluminescence bands at +20°C and + 10°C were strongly inhibited, while normal electron transport activity was retained. This indicates that the concentrations of S2 and S3 states involved in the generation of these bands are reduced. At higher concentrations, an increased activity of electron transport was observed, which is attributed to the typical uncoupler effect of protonophores. Indeed, acridones accelerate the decay of the electrochromic absorbance change at 515 nm and also inhibit the generation of the transmembrane proton gradient, measured as an absorbance transient of neutral red. Variable fluorescence induction was quenched even at low concentrations of acridones but was restored by either a long-term illumination or high light intensity. Acridones, similarly to other protonophores, promoted the autooxidation of the high-potential form of cytochrome b559 and partially converted it to lower potential forms. These results suggest that acridones, acting as typical protonophores, uncouple electron transport, accelerate the deactivation of the S2 and S3 states on the donor side, and facilitate the oxidation of cytochrome b559 on the acceptor side of photosystem II.

Original languageEnglish
Pages (from-to)3876-3880
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Volume93
Issue number9
DOIs
Publication statusPublished - Apr 30 1996

Fingerprint

Acridones
Proton Ionophores
Electron Transport
Neutral Red
Photosystem II Protein Complex
Lighting
Protons
Fluorescence
Light

Keywords

  • electron transport
  • ionophores
  • photosynthesis
  • uncouplers

ASJC Scopus subject areas

  • Genetics
  • General

Cite this

Acridones : A chemically new group of protonophores. / Horváth, G.; Droppa, M.; Fodorpataki, L.; Istókovics, A.; Garab, G.; Oettmeier, W.

In: Proceedings of the National Academy of Sciences of the United States of America, Vol. 93, No. 9, 30.04.1996, p. 3876-3880.

Research output: Contribution to journalArticle

Horváth, G. ; Droppa, M. ; Fodorpataki, L. ; Istókovics, A. ; Garab, G. ; Oettmeier, W. / Acridones : A chemically new group of protonophores. In: Proceedings of the National Academy of Sciences of the United States of America. 1996 ; Vol. 93, No. 9. pp. 3876-3880.
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