Photo-reduction of flavin mononucleotide to semiquinone form in LOV domain mutants of blue-light receptor phot from Chlamydomonas reinhardtii

J Photochem Photobiol B. 2007 Apr 2;87(1):37-48. doi: 10.1016/j.jphotobiol.2006.12.007. Epub 2007 Jan 10.

Abstract

The photo-excitation dynamics of the mutants LOV1-C57S and LOV2-C250S of the LOV-domains of the phototropin photoreceptor phot from the green alga Chlamydomonas reinhardtii is investigated by absorption and fluorescence studies. The LOV domains fused to a maltose binding protein (MBP) are expressed in Escherichia coli. The mutants were studied under aerobic conditions in aqueous solution at pH 8. Blue-light exposure reduced the fully oxidized flavin mononucleotide, FMN(ox), to FMN semiquinone, FMNH*, (quantum efficiency around 1%) which further reduced to FMN hydroquinone, FMN(red)H(2) or FMN(red)H(-) (quantum efficiency ca. 3 x 10(-5)). In the dark both reduced forms recovered back to the oxidized form on a minute timescale. Besides photoreduction, blue-light photo-excitation of the mutants resulted in photoproduct formation (efficiency in the 2 x 10(-4) - 10(-3) range). Photo-reaction schemes for the mutants are discussed.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Benzoquinones / analysis*
  • Benzoquinones / radiation effects
  • Chlamydomonas reinhardtii / genetics
  • Chlamydomonas reinhardtii / radiation effects*
  • Flavin Mononucleotide / metabolism
  • Flavin Mononucleotide / radiation effects*
  • Mutation
  • Oxidation-Reduction

Substances

  • Benzoquinones
  • semiquinone radicals
  • Flavin Mononucleotide