Project description:Identification of the proteins from tryptic digests of Metallosphaera cuprina strain Ar-4 whole-cell proteome followed by nanoLC/OrbitrapFusion MS analysis.
Project description:By using heterotrophic proteome as reference, 169 proteins were found to change their abundance during autotrophic growth. The up-regulated proteins indicated that M. cuprina fixed CO2 through the previously identified 3-HB-CoA/4-HB-CoA cycle and obtained energy by oxidation of elemental sulfur as energy source under autotrophic growth. Enzymes/proteins involved in semi- and non-phosphorylating Entner-Doudoroff (ED) pathway were down-regulated. We also found that some transporter proteins changed their abundances, suggest that they were likely playing pivotal roles for growth under the respective conditions.
Project description:Tetrathionate hydrolase (TTH) is a key enzyme for the oxidation of reduced inorganic sulfur compounds (RISCs) with the S4I pathway, which is distributed in autotrophic or facultative autotrophic sulfur-oxidizing bacteria and archaea. In this study, the enzyme TTHMc from the acidothermophilic archaeon Metallosphaera cuprina Ar-4T, encoded by mcup_1281 and belonging to the pyrroloquinoline quinone (PQQ) family, has been shown to possess tetrathionate hydrolysis activity. The molecular mass of the single subunit of TTHMc was determined to be 57 kDa. TTHMc is proved to be located in the cytoplasm, periplasmic space, and membrane, and the activity of them accounted for 72.3%, 24.0%, and 3.7% of the total activity. Optimal activity was observed at temperatures above 95 °C and pH 6.0, and the kinetic constants Km and Vmax were 0.35 mmol/L and 86.3 μmol/L, respectively. The presence of 0.01 mol/L Mg2+ enhances the activity of TTHMc, while 0.01 mol/L Ca2+ inhibits its activity. The hydrolysis of tetrathionate (TT) by TTHMc results in the production of thiosulfate, pentathionate, and hexathionate. This study represents the first description of TTH in the genus Metallosphaera, providing new theoretical insights into the study of sulfur-oxidizing proteins in acidothermophilic archaea.
