Chemical and Environmental Science Department, Materials and Surface Science Institute, University of Limerick, Limerick, Ireland.
J Bacteriol. 2011 Aug;193(15):3988-97. doi: 10.1128/JB.05186-11. Epub 2011 Jun 10.
Sulfite, produced for instance during amino acid metabolism, is a very reactive and toxic compound. Various detoxification mechanisms exist, but sulfite oxidoreductases (SORs) are one of the major actors in sulfite remediation in bacteria and animals. Here we describe the existence of an operon in the extreme thermophilic bacterium Thermus thermophilus HB8 encoding both a SOR and a diheme c-type cytochrome. The in vitro analysis clearly showed that the newly identified cytochrome c₅₅₀ acts as an acceptor of the electrons generated by the SOR enzyme during the oxidation of sulfite. The electrons are then rapidly shuttled via cytochrome c₅₅₂ to the terminal ba₃- and caa₃-type oxidases, thereby unveiling a novel electron transfer pathway, linking sulfite oxidation to oxygen reduction in T. thermophilus: sulfite → SOR(HB8) → cytochrome c₅₅₀ → cytochrome c₅₅₂ → ba₃ oxidase/caa₃ oxidase → O₂. The description of the complete pathway reveals that electrons generated during sulfite oxidation by the SOR are funneled into the respiratory chain, participating in the energy production of T. thermophilus.
亚硫酸盐是一种非常活跃和有毒的化合物，例如在氨基酸代谢过程中产生。存在各种解毒机制，但亚硫酸盐氧化还原酶（SOR）是细菌和动物中亚硫酸盐修复的主要因素之一。在这里，我们描述了极端嗜热细菌 Thermus thermophilus HB8 中的一个操纵子的存在，该操纵子编码 SOR 和二血红素 c 型细胞色素。体外分析清楚地表明，新鉴定的细胞色素 c₅₅₀在 SOR 酶氧化亚硫酸盐期间作为电子的受体起作用。然后，电子通过细胞色素 c₅₅₂迅速转移至末端 ba₃-和 caa₃-型氧化酶，从而揭示了一种新的电子传递途径，将亚硫酸盐氧化与 Thermus thermophilus 中的氧还原联系起来：亚硫酸盐→SOR（HB8）→细胞色素 c₅₅₀→细胞色素 c₅₅₂→ba₃氧化酶/caa₃氧化酶→O₂。完整途径的描述表明，SOR 氧化亚硫酸盐过程中产生的电子被引导到呼吸链中，参与 Thermus thermophilus 的能量产生。
