Scientific article

The chloroplast ycf7 (petL) open reading frame of Chlamydomonas reinhardtii encodes a small functionally important subunit of the cytochrome b6f complex

Published inEMBO Journal, vol. 15, no. 14, p. 3498-3506
Publication date1996

The small chloroplast open reading frame ORF43 (ycf7) of the green unicellular alga Chlamydomonas reinhardtii is cotranscribed with the psaC gene and ORF58. While ORF58 has been found only in the chloroplast genome of C.reinhardtii, ycf7 has been conserved in land plants and its sequence suggests that its product is a hydrophobic protein with a single transmembrane alpha helix. We have disrupted ORF58 and ycf7 with the aadA expression cassette by particle-gun mediated chloroplast transformation. While the ORF58::aadA transformants are indistinguishable from wild type, photoautotrophic growth of the ycf7::aadA transformants is considerably impaired. In these mutant cells, the amount of cytochrome b₆f complex is reduced to 25-50% of wild-type level in mid-exponential phase, and the rate of transmembrane electron transfer per b₆f complex measured in vivo under saturating light is three to four times slower than in wild type. Under subsaturating light conditions, the rate of the electron transfer reactions within the b₆f complex is reduced more strongly in the mutant than in the wild type by the proton electrochemical gradient. The ycf7 product (Ycf7) is absent in mutants deficient in cytochrome b₆f complex and present in highly purified b₆f complex from the wild-type strain. Ycf7-less complexes appear more fragile than wild-type complexes and selectively lose the Rieske iron-sulfur protein during purification. These observations indicate that Ycf7 is an authentic subunit of the cytochrome b₆f complex, which is required for its stability, accumulation and optimal efficiency. We therefore propose to rename the ycf7 gene petL.

  • Amino acid sequence
  • Animals
  • Base sequence
  • Chlamydomonas reinhardtii/enzymology/genetics
  • Chloroplasts/genetics
  • Cytochrome b group/genetics/metabolism
  • Cytochrome b6f complex
  • Electron transport
  • Electron transport complex III
  • Enzyme stability
  • Gene deletion
  • Iron-sulfur proteins/metabolism
  • Light
  • Molecular sequence data
  • Open reading frames
  • Operon
  • Protons
  • Rabbits
  • Transformation
  • Genetic
  • Swiss National Science Foundation - 31.34014.92
Citation (ISO format)
TAKAHASHI, Yuichiro et al. The chloroplast <i>ycf7</i> (<i>petL</i>) open reading frame of <i>Chlamydomonas reinhardtii</i> encodes a small functionally important subunit of the cytochrome <i>b<sub>6</sub>f</i> complex. In: EMBO Journal, 1996, vol. 15, n° 14, p. 3498–3506.
Main files (1)
Article (Published version)
ISSN of the journal0261-4189

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