Proteomic Analysis of Hydrogen Photoproduction in Sulfur-Deprived Chlamydomonas Cells

The green alga Chlamydomonas reinhardtii is a model organism to study H₂ metabolism in photosynthetic eukaryotes. To understand the molecular mechanism of H₂ metabolism, we used 2-DE coupled with MALDI-TOF and MALDI-TOF/TOF-MS to investigate proteomic changes of Chlamydomonas cells that undergo sulfur-depleted H₂ photoproduction process. In this report, we obtained 2-D PAGE soluble protein profiles of Chlamydomonas at three time points representing different phases leading to H₂ production. We found over 105 Coomassie-stained protein spots, corresponding to 82 unique gene products, changed in abundance throughout the process. Major changes included photosynthetic machinery, protein biosynthetic apparatus, molecular chaperones, and 20S proteasomal components. A number of proteins related to sulfate, nitrogen and acetate assimilation, and antioxidative reactions were also changed significantly. Other proteins showing alteration during the sulfur-depleted H₂ photoproduction process were proteins involved in cell wall and flagella metabolisms. In addition, among these differentially expressed proteins, 11 were found to be predicted proteins without functional annotation in the Chlamydomonas genome database. The results of this proteomic analysis provide new insight into molecular basis of H₂ photoproduction in Chlamydomonas under sulfur depletion.