Photosynthesis Research

, Volume 83, Issue 3, pp 329–333 | Cite as

Cyanobacterial Photosystem I lacks specificity in its interaction with cytochrome c6 electron donors

  • Manuel Hervás
  • Antonio Díaz-Quintana
  • Cheryl A. Kerfeld
  • David W. Krogmann
  • Miguel A. De la Rosa
  • José A. Navarro
Regular paper


In cyanobacteria, plastocyanin and cytochrome c6, the alternate donor proteins to Photosystem I, can be acidic, neutral or basic; the role of electrostatics in their interaction with photosystem I varies accordingly. In order to elucidate whether these changes in the electron donors’ properties correlate with complementary changes in the docking site of the corresponding photosystem, we have investigated the kinetics of reactions between three cytochrome c6 with isoelectric points of 5.6, 7.0 and 9.0, with Photosystem I particles from the same three genera of cyanobacteria which provided the cytochromes. The model systems compared here thus sample the full range of charge properties observed in cytochromes c6: acidic, basic and neutral. The rate constants and dependence on ionic strength for photosystem I reduction were distinctive for each cytochrome c6, but independent of Photosystem I. We conclude that the specific structural features of each cytochrome c6 dictate their different kinetic behaviours, whereas the three photosystems are relatively indiscriminate in docking with the electron donors.


Arthrospira cytochrome c6 laser flash photolysis Nostoc Photosystem I Synechocystis 


Cyt c6

cytochrome c6


second order rate constant


observed pseudo first-order rate constant


Photosystem I


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Copyright information

© Springer 2005

Authors and Affiliations

  • Manuel Hervás
    • 1
  • Antonio Díaz-Quintana
    • 1
  • Cheryl A. Kerfeld
    • 2
  • David W. Krogmann
    • 3
  • Miguel A. De la Rosa
    • 1
  • José A. Navarro
    • 1
  1. 1.Instituto de Bioquímica Vegetal y Fotosíntesis, Centro de Investigaciones Científicas Isla de la CartujaUniversidad de Sevilla y CSICSevillaSpain
  2. 2.Molecular Biology InstituteUCLALos AngelesUSA
  3. 3.Department of BiochemistryPurdue UniversityWest LafayetteUSA

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