The sole cysteine residue (Cys301) of tetrathionate hydrolase from Acidithiobacillus ferrooxidans does not play a role in enzyme activity

Tadayoshi Kanao, Hisayuki Nakayama, Mizuki Kato, Kazuo Kamimura

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)

Abstract

Cysteine residues are absolutely indispensable for the reactions of almost all enzymes involved in the dissimilatory oxidation pathways of reduced inorganic sulfur compounds. Tetrathionate hydrolase from the acidophilic iron- and sulfur-oxidizing bacterium Acidithiobacillus ferrooxidans (Af-Tth) catalyzes tetrathionate hydrolysis to generate elemental sulfur, thiosulfate, and sulfate. Af-Tth is a key enzyme in the dissimilatory sulfur oxidation pathway in this bacterium. Only one cysteine residue (Cys301) has been identified in the deduced amino acid sequence of the Af-Tth gene. In order to clarify the role of the sole cysteine residue, a site-specific mutant enzyme (C301A) was generated. No difference was observed in the retention volumes of the wild-type and mutant Af -Tth enzymes by gel-filtration column chromatography, and surprisingly the enzyme activities measured in the cysteine-deficient and wild-type enzymes were the same. These results suggest that the sole cysteine residue (Cys301) in Af-Tth is involved in neither the tetrathionate hydrolysis reaction nor the subunit assembly. Af -Tth may thus have a novel cysteine-independent reaction mechanism.

Original languageEnglish
Pages (from-to)2030-2035
Number of pages6
JournalBioscience, Biotechnology and Biochemistry
Volume78
Issue number12
DOIs
Publication statusPublished - 2014

Keywords

  • Acidithiobacillus ferrooxidans
  • Cysteine residue
  • Sulfur metabolism
  • Tetrathionate hydrolase

ASJC Scopus subject areas

  • Biotechnology
  • Analytical Chemistry
  • Biochemistry
  • Applied Microbiology and Biotechnology
  • Molecular Biology
  • Organic Chemistry

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