The sole cysteine residue (Cys301) of tetrathionate hydrolase from Acidithiobacillus ferrooxidans does not play a role in enzyme activity
The sole cysteine residue (Cys301) of tetrathionate hydrolase from Acidithiobacillus ferrooxidans does not play a role in enzyme activity
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DOI：
10.1080/09168451.2014.948374
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发表时间：
2014-12
期刊：
影响因子：
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通讯作者：
T. Kanao;Hisayuki Nakayama;Mizuki Kato;K. Kamimura
中科院分区：
文献类型：
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作者：
T. Kanao;Hisayuki Nakayama;Mizuki Kato;K. Kamimura
半胱氨酸残基对于几乎所有参与还原无机硫化合物的异化氧化途径的酶的反应是绝对不可缺少的。来自嗜酸性铁和硫氧化细菌Acidithiobacillus ferrooxidans（Af-Tth）的连四硫酸盐水解酶催化连四硫酸盐水解以产生元素硫、硫代硫酸盐和硫酸盐。Af-Tth是该细菌异化硫氧化途径中的关键酶。在推导的Af-Tth基因的氨基酸序列中仅鉴定出一个半胱氨酸残基（Cys 301）。为了阐明唯一半胱氨酸残基的作用，产生了位点特异性突变酶（C301 A）。通过凝胶过滤柱色谱法在野生型和突变体Af-Tth酶的保留体积中没有观察到差异，并且令人惊讶的是，在半胱氨酸缺陷型和野生型酶中测量的酶活性是相同的。这些结果表明，唯一的半胱氨酸残基（Cys 301）在Af-Tth既不参与连四硫酸盐水解反应，也不参与亚基组装。因此，Af-Tth可能具有新的半胱氨酸非依赖性反应机制。图形摘要Af-Tth中唯一的半胱氨酸残基（Cys 301）既不参与连四硫酸盐水解反应，也不参与亚基组装。
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. Graphical Abstract The sole cysteine residue (Cys301) in Af-Tth is not involved in neither the tetrathionate hydrolysis reaction nor subunit assembly.