Phosphoproteomic analysis of methanoarchaeon Methanohalophilus portucalensis FDF1T reveals diverse functions in methanogenesis and osmoadaptation

Methane is a well-known factor in green house effect and also could be an alternative energy, which produced via methanogenesis by methanogenic archaea. Methanohalophilus portucalensis FDF1T is a halophilic methylotrophic methanogen and has been used as a model to study osmoadaptation in fluctuated abiotic environmental conditions. Here we report a genome-wide phosphoproteomic analysis of M. portucalensis FDF1T to uncover the possible phosphorylation-mediated regulations in methanogenesis and osmoadaptation. According to the biological function analysis revealed 20.6% of total 149 phosphoproteins were involved in the regulation of the single carbon metabolism for methanogenesis and osmoadaptation. Together with genome sequencing and phosphoproteomic analysis, we provided the first evidence to indicate protein phosphorylation networks in regulating the pyrrolysine (Pyl) mediated translation of methylotrophic methyltransferase. Furthermore, the functional assays of glycine sarcosine N-methyltransferase revealed that the enzymatic activity was modulated by threonine phosphorylation. Collectively, our results not only provide new insight into phosphorylation-mediated regulations in single carbon energy metabolism but also clearly demonstrate that phosphorylation plays a critical role in osmolyte betaine synthesis through a phospho-switch mechanism.