Structural and functional changes of PSI-LHCI supercomplexes of Chlamydomonas reinhardtii cells grown under high salt conditions

Rajagopal Subramanyam, Craig Jolley, Balakumar Thangaraj, Sreedhar Nellaepalli, Andrew N. Webber, Petra Fromme

Research output: Contribution to journalArticle

14 Citations (Scopus)

Abstract

The effect of high salt concentration (100 mM NaCl) on the organization of photosystem I-light harvesting complex I supercomplexes (PSI-LHCI) of Chlamydomonas reinhardtii was studied. The electron transfer activity was reduced by 39% in isolated PSI-LHCI supercomplexes. The visible circular dichroism (CD) spectra associated with strongly coupled chlorophyll (Chl) dimers were reduced in intensity, indicating that pigment-pigment interactions were disrupted. This data is consistent with results from fluorescence streak camera spectroscopy, which suggest that red-shifted pigments in the PSI-LHCI antenna had been lost. Denaturing gel electrophoresis and immunoblot analysis reveals that levels of the PSI reaction center proteins PsaD, PsaE and PsaF were reduced due to salt stress. PsaE is almost completely absent under high salt conditions. It is known that the membrane-extrinsic subunits PsaD and E form the ferredoxin-docking site. Our results indicate that the PSI-LHCI supercomplex is damaged by reactive oxygen species at high salt concentration, with particular impact on the ferredoxin-docking site and the PSI-LHCI interface.

Original languageEnglish
Pages (from-to)913-922
Number of pages10
JournalPlanta
Volume231
Issue number4
DOIs
Publication statusPublished - Mar 1 2010
Externally publishedYes

Keywords

  • Chlamydomonas
  • Excitation energy
  • Light harvesting complexes
  • PSI-LHCI supercomplexes
  • Photosystem I core
  • Reactive oxygen species
  • Salt stress
  • Superoxide dismutase

ASJC Scopus subject areas

  • Genetics
  • Plant Science

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