The elongator subunit Elp3 contains a Fe4S4 cluster and binds S-adenosylmethionine
The elongator subunit Elp3 contains a Fe4S4 cluster and binds S-adenosylmethionine
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DOI：
10.1111/j.1365-2958.2005.04989.x
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发表时间：
2006-02-01
影响因子：
3.6
通讯作者：
Onesti, S
中科院分区：
文献类型：
--
作者：
Paraskevopoulou, C;Fairhurst, SA;Onesti, S
Elongator 复合体的 Elp3 亚基从古细菌到人类都高度保守，并且包含一个明确的 C 端组蛋白乙酰转移酶 (HAT) 结构域。 Elp3 的中心区域与 Radical SAM 超家族具有显着的序列同源性。这个细菌蛋白大家族的成员含有 FeS 簇，并使用 S-腺苷甲硫氨酸 (SAM) 催化各种自由基反应。为了对该结构域进行生化表征，我们表达并纯化了詹氏甲烷球菌 Elp3 蛋白的相应片段。 Fe4S4 簇的存在已通过紫外-可见光谱和电子顺磁共振 (EPR) 光谱得到证实，并且 Fe 含量通过比色测定和原子吸收光谱测定。已通过定点诱变鉴定了参与簇形成的半胱氨酸残基。该蛋白质与 SAM 结合，并且这种结合改变了 FeS 簇的 EPR 光谱。我们的结果为以下假设提供了生化支持：Elp3 确实含有表征 Radical SAM 超家族的 Fe4S4 簇并结合 SAM，表明 Elp3 除了其 HAT 活性外，还具有第二个尚未表征的催化功能。我们还提供了初步数据来表明该蛋白质可切割 SAM。
The Elp3 subunit of the Elongator complex is highly conserved from archaea to humans and contains a well-characterized C-terminal histone acetyltransferase (HAT) domain. The central region of Elp3 shares significant sequence homology to the Radical SAM superfamily. Members of this large family of bacterial proteins contain a FeS cluster and use S-adenosylmethionine (SAM) to catalyse a variety of radical reactions. To biochemically characterize this domain we have expressed and purified the corresponding fragment of the Methanocaldococcus jannaschii Elp3 protein. The presence of a Fe4S4 cluster has been confirmed by UV-visible spectroscopy and electron paramagnetic resonance (EPR) spectroscopy and the Fe content determined by both a colorimetric assay and atomic absorption spectroscopy. The cysteine residues involved in cluster formation have been identified by site-directed mutagenesis. The protein binds SAM and the binding alters the EPR spectrum of the FeS cluster. Our results provide biochemical support to the hypothesis that Elp3 does indeed contain the Fe4S4 cluster which characterizes the Radical SAM superfamily and binds SAM, suggesting that Elp3, in addition to its HAT activity, has a second as yet uncharacterized catalytic function. We also present preliminary data to show that the protein cleaves SAM.