Site-directed mutations affecting the spectroscopic characteristics and midpoint potential of the primary donor in photosystem I

Andrew Webber, Hui Su, Scott E. Bingham, Hanno Käss, Ludwig Krabben, Matthias Kuhn, Rafael Jordan, Eberhard Schlodder, Wolfgang Lubitz

Research output: Contribution to journalArticlepeer-review

63 Scopus citations

Abstract

Photosystem I is a member of the iron-sulfur center or type I reaction centers. The primary electron donor in photosystem I is a chlorophyll a dimer termed P700. The biophysical properties of P700 are well understood, but the protein environment that gives it such unique properties is unknown. We have characterized site-directed mutants of the photosystem I reaction center protein PsaB and identified an amino acid, His-656, that interacts closely with one of the P700 chlorophylls. Mutation of His-656 to Asn or Ser increases the oxidation midpoint potential of P700/P700+· by 40 mV. The P700/P700+· optical difference spectra show the appearance of a new bleaching band at 667 nm. Electron nuclear double resonance spectroscopy indicates a significant increase in the hyperfine coupling corresponding to methyl protons at position 12 of the spin carrying chlorophyll a of P700+·. The implication of these results to current structural models of the photosystem I reaction center is discussed.

Original languageEnglish (US)
Pages (from-to)12857-12863
Number of pages7
JournalBiochemistry
Volume35
Issue number39
DOIs
StatePublished - Oct 19 1996

ASJC Scopus subject areas

  • Biochemistry

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