Small subunits of Photosystem I reaction center complexes from Synechococcus elongatus. I. Is the psaF gene product required for oxidation of cytochrome c-553?

Hideki Hatanaka, Kintake Sonoike, Masahiko Hirano, Sakae Katoh

Research output: Contribution to journalArticle

42 Citations (Scopus)

Abstract

Photosystem I (PS I) reaction center complexes isolated from the thermophilic cyanobacterium Synechococcus elongatus with nonionic detergents, digitonin or sucrose monolaurate, contained eight small subunit polypeptides. Two of the small polypeptides were identified by analysis of their N-terminal amino-acid sequences as the psaF and psaE gene products. Treatment with a cationic detergent, cetyltrimethylammonium bromide, resulted in depletion of five small subunits including the psaF gene product. Five PS I complexes isolated with an anionic detergent, sodium dodecylsulfate, contained zero to four small subunits but were all depleted of the psaF polypeptide. The function of the psaF gene product was examined by measuring reduction kinetics of flash-oxidized P-700 in the presence of different concentrations of cytochrome c-553. Oxidized P-700 was rapidly reduced by the reduced cytochrome in all the PS I complexes that contained, at least, the psaC and psaD polypeptides and the second-order rate constants of electron transfer from cytochrome c-553 to P-700 were essentially the same between PS I complexes that contained the psaF polypeptide and those that lost this polypeptide. Thus, the psaF polypeptide is not required for the bimolecular reaction between P-700 and cytochrome c-553. Mg2+ had a moderate stimulating effect on the rate of P-700 reduction whether PS I complexes were associated with the psaF gene product or not. The function of this subunit polypeptide is discussed.

Original languageEnglish
Pages (from-to)45-51
Number of pages7
JournalBBA - Bioenergetics
Volume1141
Issue number1
DOIs
Publication statusPublished - 1993 Feb 8
Externally publishedYes

Keywords

  • (S. elongatus)
  • Cytochrome c-553
  • Detergent
  • Photosystem I
  • Reaction center complex
  • Subunit
  • psaF gene

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Cell Biology

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