Identification of a Rhodobacter capsulatus L-Cysteine desulfurase that sulfurates the molybdenum cofactor when bound to XdhC and before its insertion into xanthine dehydrogenase
Identification of a Rhodobacter capsulatus L-Cysteine desulfurase that sulfurates the molybdenum cofactor when bound to XdhC and before its insertion into xanthine dehydrogenase
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DOI：
10.1021/bi700630p
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发表时间：
2007-08-21
期刊：
影响因子：
2.9
通讯作者：
Leimkuehler, Silke
中科院分区：
文献类型：
--
作者：
Neumann, Meina;Stoecklein, Walter;Leimkuehler, Silke
含有醛氧化酶和黄嘌呤脱氢酶的钼辅因子（Moco）需要在Moco中插入末端硫配体的硫化步骤才能产生活性。XdhC被证明是在荚膜红杆菌中产生活性XDH所必需的，但它本身不是纯化酶的亚基。XdhC结合化学计量量的Moco，并进一步能够将其结合的Moco转移到XDH。先前的研究表明，在插入XDH之前，XdhC特别稳定了硫化形式的Moco。在这项工作中，我们鉴定了一种荚膜霉l -半胱氨酸脱硫酶NifS4，它参与了Moco的MoS配体的形成。我们发现NifS4与XdhC相互作用，而不是与XDH相互作用。NifS4通过形成与蛋白质结合的过硫中间体从l -半胱氨酸中动员硫，并将这些硫进一步转移到Moco。该反应比以硫化物为硫源的Moco化学硫化反应更有效。进一步的研究清楚地表明，Moco在插入XDH之前是硫化的，而它与XdhC结合。综上所述，XdhC在荚膜霉中具有多种作用：与Moco结合，与NifS4相互作用使Moco硫化，保护硫化后的Moco免于氧化，并进一步转移到XDH。
The molybdenum cofactor (Moco) containing enzymes aldehyde oxidase and xanthine dehydrogenase (XDH) require for activity a sulfuration step that inserts a terminal sulfur ligand into Moco. XdhC was shown to be essential for the production of active XDH in Rhodobacter capsulatus but is itself not a subunit of the purified enzyme. XdhC binds stoichiometric amounts of Moco and is further able to transfer its bound Moco to XDH. Previous work suggested that XdhC particularly stabilizes the sulfurated form of Moco before the insertion into XDH. In this work, we identify an R. capsulatus L-cysteine desulfurase, NifS4, which is involved in the formation of the MoS ligand of Moco. We show that NifS4 interacts with XdhC and not with XDH. NifS4 mobilizes sulfur from L-cysteine by formation of a protein-bound persulfide intermediate and transfers this sulfur further to Moco. This reaction was shown to be more effective than the chemical sulfuration of Moco using sulfide as sulfur source. Further studies clearly showed that Moco is sulfurated before the insertion into XDH, while it is bound to XdhC. Conclusively, XdhC has a versatile role in R. capsulatus: binding of Moco, interaction with NifS4 for the sulfuration of Moco, protection of sulfurated Moco from oxidation, and further transfer to XDH.