Excitation energy transfer in thylakoid membranes from Chlamydomonas reinhardtii lacking chlorophyll b and with mutant Photosystem I

Alexander N. Melkozernov, Hui Su, Andrew Webber, Robert E. Blankenship

Research output: Contribution to journalArticle

11 Scopus citations

Abstract

Energy trapping in Photosystem I (PS I) was studied by time-resolved fluorescence spectroscopy of PS II-deleted Chl b-minus thylakoid membranes isolated from site-directed mutants of Chlamydomonas reinhardtii with specific amino acid substitutions of a histidine ligand to P700. In vivo the fluorescence of the PS I core antenna in mutant thylakoids with His-656 of PsaB replaced by asparagine, serine or phenylalanine is characterized by an increase in the lifetime of the fast decay component ascribed to the energy trapping in PS I (25 ps in wild type PS I with intact histidine-656, 50 ps in the mutant PS I with asparagine-656 and 70 ps in the mutant PS I with phenylalanine-656). Assuming that the excitation dynamics in th PS I antenna are trap-limited, the increase in the trapping time suggests a decrease in the primary charge separation rate. Western blot analysis showed that the mutants accumulate significantly less PS I than wild type. Spectroscopically, the mutations lead to a decrease in relative quantum yield of the trapping in the PS I core and increase in relative quantum yield of the fluorescence decay phase ascribed to uncoupled chlorophyll-protein complexes which suggests that improper assembly of PS I and LHC in the mutant thylakoids may result in energy uncoupling in PS I.

Original languageEnglish (US)
Pages (from-to)197-207
Number of pages11
JournalPhotosynthesis research
Volume56
Issue number2
DOIs
StatePublished - Jan 1 1998

Keywords

  • Energy transfer kinetics
  • Energy uncoupling
  • P
  • Photosystem I (Chlamydomonas reinhardtii)
  • Site-directed mutants
  • Thylakoids
  • Time-resolved fluorescence

ASJC Scopus subject areas

  • Biochemistry
  • Plant Science
  • Cell Biology

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