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Configuration of Ten Light-Harvesting Chlorophyll a / b Complex I Subunits in Chlamydomonas reinhardtii Photosystem I.
- Source :
-
Plant physiology [Plant Physiol] 2018 Oct; Vol. 178 (2), pp. 583-595. Date of Electronic Publication: 2018 Aug 20. - Publication Year :
- 2018
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Abstract
- In plants, the photosystem I (PSI) core complex stably associates with its light-harvesting chlorophyll a / b complex I (LHCI) to form the PSI-LHCI supercomplex. The vascular plant PSI core complex associates with four distinct LHCI subunits, whereas that of the green alga Chlamydomonas reinhardtii binds nine distinct LHCI subunits (LHCA1-LHCA9). The stoichiometry and configuration of these LHCI subunits in the PSI-LHCI supercomplex of C. reinhardtii remain controversial. Here, we determined the stoichiometry of the nine distinct LHCI subunits relative to PSI subunits through uniform labeling of total proteins using <superscript>14</superscript> C. We separated the nine LHCI polypeptides by three different sodium dodecyl sulfate-polyacrylamide gel electrophoresis systems. Our data revealed that the PSI-LHCI supercomplex contains two LHCA1 proteins and one of each of the other eight LHCI subunits. Subsequently, we identified their cross-linked products by immunodetection and mass spectrometry to determine the configuration of the 10 LHCI subunits within the PSI-LHCI supercomplex. Furthermore, analyses of PSI-LHCI complexes isolated from Δ LHCA2 and Δ LHCA5 mutants and oligomeric LHCI from a PSI-deficient (Δ psaA / B ) mutant provided supporting evidence for the LHCI subunit configuration. In conclusion, eight LHCI subunits bind to the PSI core at the site of PSAF subunit in two layers: LHCA1-LHCA8-LHCA7-LHCA3 from PSAG to PSAK, in the inner layer, and LHCA1-LHCA4-LHCA6-LHCA5 in the outer layer. The other two LHCI subunits, LHCA2 and LHCA9, bind PSAB between PSAG and PSAH, PSAG-LHCA9-LHCA2-PSAH. Our study provides new insights into the LHCI configuration linked to the PSI core.<br /> (© 2018 The author(s). All Rights Reserved.)
- Subjects :
- Chlamydomonas reinhardtii genetics
Chlorophyll metabolism
Chlorophyll A metabolism
Immunochemistry
Mutation
Photosystem I Protein Complex genetics
Tandem Mass Spectrometry
Chlamydomonas reinhardtii metabolism
Light-Harvesting Protein Complexes metabolism
Models, Structural
Photosystem I Protein Complex metabolism
Subjects
Details
- Language :
- English
- ISSN :
- 1532-2548
- Volume :
- 178
- Issue :
- 2
- Database :
- MEDLINE
- Journal :
- Plant physiology
- Publication Type :
- Academic Journal
- Accession number :
- 30126869
- Full Text :
- https://doi.org/10.1104/pp.18.00749