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Scientific article
Open access
English

The N-terminal domain of PsaF: precise recognition site for binding and fast electron transfer from cytochrome c6 and plastocyanin to photosystem I of Chlamydomonas reinhardtii

Publication date1998-06-23
Abstract

The PsaF-deficient mutant 3bF of Chlamydomonas reinhardtii was used to modify PsaF by nuclear transformation and site-directed mutagenesis. Four lysine residues in the N-terminal domain of PsaF, which have been postulated to form the positively charged face of a putative amphipathic alpha-helical structure were altered to K12P, K16Q, K23Q, and K30Q. The interactions between plastocyanin (pc) or cytochrome c6 (cyt c6) and photosystem I (PSI) isolated from wild type and the different mutants were analyzed using crosslinking techniques and flash absorption spectroscopy. The K23Q change drastically affected crosslinking of pc to PSI and electron transfer from pc and cyt c6 to PSI. The corresponding second order rate constants for binding of pc and cyt c6 were reduced by a factor of 13 and 7, respectively. Smaller effects were observed for mutations K16Q and K30Q, whereas in K12P the binding was not changed relative to wild type. None of the mutations affected the half-life of the microsecond electron transfer performed within the intermolecular complex between the donors and PSI. The fact that these single amino acid changes within the N-terminal domain of PsaF have different effects on the electron transfer rate constants and dissociation constants for both electron donors suggests the existence of a rather precise recognition site for pc and cyt c6 that leads to the stabilization of the final electron transfer complex through electrostatic interactions.

eng
Keywords
  • Animals
  • Binding Sites
  • Chlamydomonas reinhardtii / genetics
  • Chlamydomonas reinhardtii / metabolism
  • Chlorophyll / metabolism
  • Cytochromes / metabolism
  • Cytochromes f
  • Electron Transport
  • Kinetics
  • Light-Harvesting Protein Complexes
  • Membrane Proteins / chemistry
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism
  • Photosynthetic Reaction Center Complex Proteins / genetics
  • Photosystem I Protein Complex
  • Plastocyanin / metabolism
  • Protozoan Proteins
Citation (ISO format)
HIPPLER, Michael et al. The N-terminal domain of PsaF: precise recognition site for binding and fast electron transfer from cytochrome c<sub>6</sub> and plastocyanin to photosystem I of <i>Chlamydomonas reinhardtii</i>. In: Proceedings of the National Academy of Sciences of the United States of America, 1998, vol. 95, n° 13, p. 7339–7344. doi: 10.1073/pnas.95.13.7339
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Article (Published version)
Identifiers
ISSN of the journal0027-8424
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