Phosphoproteome of Rhodopseudomonas palustris
Date Issued
2010
Date
2010
Author(s)
Yi, Tsun-Hsuan
Abstract
Rhodopseudomonas palustris (R. palustris) is a purple nonsulfur anoxygenic phototrophic bacterium that belongs to the alpha-proteobacteria. It is a common soil and water bacterium that makes its living by converting sunlight to cellular energy and by absorbing atmospheric carbon dioxide and converting to biomass. This microbe can also degrade and recycle components of the woody tissues of plants. Because of its intimate involvement in carbon management and recycling, R. palustris was selected by the DOE Carbon Management Program for genome sequencing. R. palustris exhibits the ability to grow under photoheterotrophic, photoautotrophic, chemoheterotrophic and chemoautotrophic conditions, and can switch between the four different modes of metabolism for survival by protein phosphorylation. Here, we analyzed the phosphoproteome of R. palustris in photoheterotrophic condition with a shotgun approach and identified 80 phosphopeptides from 73 phosphoproteins and 74 phosphopeptides from 68 phosphoproteins at chemohetrotrophic and photoheterotrophic condition, respectively. Our results revealed that the threonine phosphorylated peptide “GGMpTSHAAVVAR” from pyruvate phosphate dikinase (PPDK, RPA1051) in photoheterotrophic condition is elevated more than 2 folds than in chemoheterotrophic condition. PPDK performs a light-dependent activity and plays an important role in carbon fixation in C4 and CAM plants. However, the function of phosphorylated PPDK is still unknown in prokaryotic cell. Here, we showed that PPDK enzyme activity is higher in photoheterotrophic than in chemoheterotrophic. In our in vitro point mutation experiment revealed that threonine phosphorylation site played an important role in regulating PPDK activity. We suggested that light could stimulate threonine phosphorylation of PPDK and might enhance its activity which could regulate the switch mechanism of R. palustris in photoheterotrophic and chemoheterotrophic conditions.
Subjects
Rhodopseudomonas palustris
phosphoproteome
phosphopeptide
photoheterotrophic
chemoheterotrophic
Type
thesis
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