Studies on the enzymatic chemistry involved in the inorganic sulfur metabolism and its application

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This study has been performed to progress our knowledge about the enzymes involved in the dissimilatory inorganic sulfur metabolism in the sulfur-oxidizing bacteria. We have isolated and identified the gene encodingtetrathionate hydrolase (Af-tth) which is the key enzyme in the metabolism in Acidithiobacillus ferrooxidans. Although Af-tthwas cloned and expressed in recombinant Escherichia coli, the recombinant proteins were synthesized in inclusion bodies as an inactive form. However, we have developed a new method to obtain the recombinant Af-Tth in an active form by refolding under acidic conditions. The enzyme was purified to homogeneity and crystallized. X-ray crystallographic analysis showed that the crystal diffracted to 2.15 A resolution and belongs to space group P31or P32with unit-cell parameters a = b= 92.1, c = 232.6 A. Further analyses such as multiple/single anomalous dispersion methods are required to determine the Af-Tth structure.