Proteomic Analysis of Hydrogen Photoproduction in Sulfur-Deprived <i>Chlamydomonas</i> Cells

The green alga <i>Chlamydomonas reinhardtii</i> is a model organism to study H<sub>2</sub> metabolism in photosynthetic eukaryotes. To understand the molecular mechanism of H<sub>2</sub> metabolism, we used 2-DE coupled with MALDI-TOF and MALDI-TOF/TOF-MS to investigate proteomic changes of <i>Chlamydomonas</i> cells that undergo sulfur-depleted H<sub>2</sub> photoproduction process. In this report, we obtained 2-D PAGE soluble protein profiles of <i>Chlamydomonas</i> at three time points representing different phases leading to H<sub>2</sub> 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 H<sub>2</sub> 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 <i>Chlamydomonas</i> genome database. The results of this proteomic analysis provide new insight into molecular basis of H<sub>2</sub> photoproduction in <i>Chlamydomonas</i> under sulfur depletion.