title: Proteomics of Chlamydomonas reinhardtii light-harvesting proteins.
abstract: With the recent development of techniques for analyzing transmembrane thylakoid proteins by two-dimensional gel electrophoresis, systematic approaches for proteomic analyses of membrane proteins became feasible. In this study, we established detailed two-dimensional protein maps of Chlamydomonas reinhardtii light-harvesting proteins (Lhca and Lhcb) by extensive tandem mass spectrometric analysis. We predicted eight distinct Lhcb proteins. Although the major Lhcb proteins were highly similar, we identified peptides which were unique for specific lhcbm gene products. Interestingly, lhcbm6 gene products were resolved as multiple spots with different masses and isoelectric points. Gene tagging experiments confirmed the presence of differentially N-terminally processed Lhcbm6 proteins. The mass spectrometric data also revealed differentially N-terminally processed forms of Lhcbm3 and phosphorylation of a threonine residue in the N terminus. The N-terminal processing of Lhcbm3 leads to the removal of the phosphorylation site, indicating a potential novel regulatory mechanism. At least nine different lhca-related gene products were predicted by comparison of the mass spectrometric data against Chlamydomonas expressed sequence tag and genomic databases, demonstrating the extensive variability of the C. reinhardtii Lhca antenna system. Out of these nine, three were identified for the first time at the protein level. This proteomic study demonstrates the complexity of the light-harvesting proteins at the protein level in C. reinhardtii and will be an important basis of future functional studies addressing this diversity.
authors.affiliation: Lehrstuhl für Pflanzenphysiologie, Friedrich-Schiller-Universität Jena, 07743 Jena, Germany.
authors.forename: Einar J
authors.initials: EJ
authors.lastname: Stauber
authors.forename: Andreas
authors.initials: A
authors.lastname: Fink
authors.forename: Christine
authors.initials: C
authors.lastname: Markert
authors.forename: Olaf
authors.initials: O
authors.lastname: Kruse
authors.forename: Udo
authors.initials: U
authors.lastname: Johanningmeier
authors.forename: Michael
authors.initials: M
authors.lastname: Hippler
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D016825:Chlamydomonas reinhardtii / Q000737:chemistry* / Q000235:genetics; D030562:Databases, Protein; D015180:Electrophoresis, Gel, Two-Dimensional; D015870:Gene Expression; D045342:Light-Harvesting Protein Complexes / Q000032:analysis*; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D010766:Phosphorylation; D045331:Photosystem I Protein Complex / Q000032:analysis; D045332:Photosystem II Protein Complex / Q000032:analysis; D010802:Phylogeny; D011499:Protein Processing, Post-Translational; D020543:Proteome / Q000032:analysis; D040901:Proteomics; D017386:Sequence Homology, Amino Acid
chemical_list: D045342:Light-Harvesting Protein Complexes; D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; D020543:Proteome