Functional implications of pigments bound to a cyanobacterial cytochrome b6f complex

Stephan Olav Wenk, Dirk Schneider, Ute Boronowsky, Cornelia Jäger, Christof Klughammer, Frank L. De Weerd, Henny Van Roon, Willem Vermaas, Jan P. Dekker, Matthias Rögner

Research output: Contribution to journalArticle

20 Scopus citations

Abstract

A highly purified cytochrome b6f complex from the cyanobacterium Synechocystis sp. PCC 6803 selectively binds one chlorophyll a and one carotenoid in analogy to the recent published structure from two other b 6f complexes. The unknown function of these pigments was elucidated by spectroscopy and site-directed mutagenesis. Low-temperature redox difference spectroscopy showed red shifts in the chlorophyll and carotenoid spectra upon reduction of cytochrome b6, which indicates coupling of these pigments with the heme groups and thereby with the electron transport. This is supported by the correlated kinetics of these redox reactions and also by the distinct orientation of the chlorophyll molecule with respect to the heme cofactors as shown by linear dichroism spectroscopy. The specific role of the carotenoid echinenone for the cytochrome b6f complex of Synechocystis 6803 was elucidated by a mutant lacking the last step of echinenone biosynthesis. The isolated mutant complex preferentially contained a carotenoid with 0, 1 or 2 hydroxyl groups (most likely 9-cis isomers of β-carotene, a monohydroxy carotenoid and zeaxanthin, respectively) instead. This indicates a substantial role of the carotenoid - possibly for strucure and assembly - and a specificity of its binding site which is different from those in most other oxygenic photosynthetic organisms. In summary, both pigments are probably involved in the structure, but may also contribute to the dynamics of the cytochrome b6f complex.

Original languageEnglish (US)
Pages (from-to)582-592
Number of pages11
JournalFEBS Journal
Volume272
Issue number2
DOIs
StatePublished - Jan 1 2005

Keywords

  • Carotenoid
  • Chlorophyll
  • Linear dichroism
  • Pigment analysis
  • Synechocystis PCC 6803

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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    Wenk, S. O., Schneider, D., Boronowsky, U., Jäger, C., Klughammer, C., De Weerd, F. L., Van Roon, H., Vermaas, W., Dekker, J. P., & Rögner, M. (2005). Functional implications of pigments bound to a cyanobacterial cytochrome b6f complex. FEBS Journal, 272(2), 582-592. https://doi.org/10.1111/j.1742-4658.2004.04501.x