Hidese Ryota, Inoue Takahiro, Imanaka Tadayuki, Fujiwara Shinsuke
Research Center for Environmental Bioscience, Graduate School of Science and Technology, Kwansei-Gakuin University, Sanda, Hyogo, 669-1337, Japan.
Mol Microbiol. 2014 Jul;93(2):331-45. doi: 10.1111/mmi.12662. Epub 2014 Jun 24.
The sulphur atoms of sulphur-containing cofactors that are essential for numerous cellular functions in living organisms originate from L-cysteine via cysteine desulphurase (CSD) activity. However, many (hyper)thermophilic archaea, which thrive in solfataric fields and are positioned near the root of the evolutionary tree of life, lack CSD orthologues. The existence of CSD orthologues in a subset of (hyper)thermophilic archaea is of interest with respect to the evolution of sulphur-trafficking systems for the cofactors. This study demonstrates that the disruption of the csd gene of Thermococcus kodakarensis, a facultative elemental sulphur (S(0))-reducing hyperthermophilic archaeon, encoding Tk-CSD, conferred a growth defect evident only in the absence of S(0), and that growth can be restored by the addition of S(0), but not sulphide. We show that the csd gene is not required for biosynthesis of thiamine pyrophosphate or molybdopterin, irrespective of the presence or absence of S(0), but is necessary for iron-sulphur cluster biosynthesis in the absence of S(0). Recombinant form of Tk-CSD expressed in Escherichia coli was obtained and it was found to catalyse the desulphuration of L-cysteine. The obtained data suggest that hyperthermophiles might benefit from a capacity for CSD-dependent iron-sulphur cluster biogenesis, which allows them to thrive outside solfataric environments.
含硫辅因子中的硫原子对生物体的众多细胞功能至关重要，其通过半胱氨酸脱硫酶（CSD）的活性源自L-半胱氨酸。然而，许多在硫磺泉中繁盛且位于生命进化树根部附近的（超）嗜热古菌缺乏CSD直系同源物。就辅因子的硫转运系统的进化而言，（超）嗜热古菌的一个子集中存在CSD直系同源物是令人感兴趣的。本研究表明，编码Tk-CSD的兼性元素硫（S(0)）还原超嗜热古菌柯达热球菌的csd基因的破坏仅在没有S(0)的情况下导致明显的生长缺陷，并且通过添加S(0)而非硫化物可以恢复生长。我们表明，无论是否存在S(0)，硫胺素焦磷酸或钼蝶呤的生物合成都不需要csd基因，但在没有S(0)的情况下，它对于铁硫簇的生物合成是必需的。获得了在大肠杆菌中表达的重组形式的Tk-CSD，并且发现它催化L-半胱氨酸的脱硫作用。所获得的数据表明，超嗜热菌可能受益于CSD依赖性铁硫簇生物合成的能力，这使它们能够在硫磺泉环境之外繁盛。
