Proteotypic profiling of LHCI from Chlamydomonas reinhardtii provides new insights into structure and function of the complex.
We used isotope dilution MS to measure the stoichiometry of light-harvesting complex I (LHCI) proteins with the photosystem I (PSI) core complex in the green alga Chlamydomonas reinhardtii. Proteotypic peptides served as quantitative markers for each of the nine gene products (Lhca1-9) and for PSI subunits. The quantitative data revealed that the LHCI antenna of C. reinhardtii contains about 7.5 +/- 1.4 subunits. It further demonstrated that the thylakoid LHCI population is heterogeneously composed and that several lhca gene products are not present in 1:1 stoichiometries with PSI. When compared with vascular plants, LHCI of C. reinhardtii possesses a lower proportion of proteins potentially contributing to far-red fluorescence emission. In general, the strategy presented is universally applicable for exploring subunit stoichiometries within the C. reinhardtii proteome.
Stauber
Einar J
EJ
Mass Spectrometry Group, Max Planck Institute for Chemical Ecology, Jena, Germany.
Busch
Andreas
A
Naumann
Bianca
B
Svatos
Ales
A
Hippler
Michael
M
D000595:Amino Acid Sequence; D000818:Animals; D017360:Arabidopsis / Q000737:chemistry / Q000378:metabolism; D002247:Carbon Isotopes / Q000737:chemistry; D016825:Chlamydomonas reinhardtii / Q000737:chemistry / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant / Q000502:physiology; D007553:Isotope Labeling; D045342:Light-Harvesting Protein Complexes / Q000032:analysis* / Q000378:metabolism; D008565:Membrane Proteins / Q000032:analysis* / Q000378:metabolism; D008969:Molecular Sequence Data; D045331:Photosystem I Protein Complex / Q000032:analysis* / Q000378:metabolism; D010940:Plant Proteins / Q000032:analysis / Q000378:metabolism; D040901:Proteomics / Q000379:methods*; D020524:Thylakoids / Q000737:chemistry / Q000378:metabolism
D002247:Carbon Isotopes; D045342:Light-Harvesting Protein Complexes; D008565:Membrane Proteins; D045331:Photosystem I Protein Complex; D010940:Plant Proteins