Structural basis for sulfur relay to RNA mediated by heterohexameric TusBCD complex
Structural basis for sulfur relay to RNA mediated by heterohexameric TusBCD complex
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DOI：
10.1016/j.str.2005.11.009
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发表时间：
2006-02-01
期刊：
影响因子：
5.7
通讯作者：
Nureki, O
中科院分区：
文献类型：
--
作者：
Numata, T;Fukai, S;Nureki, O
tRNA（Lys）、tRNA（Glu）和tRNA Gln的摆动位置34处的尿苷仅被修饰为2-硫代尿苷（s（2）U），这对于精确的密码子识别和同源氨酰-tRNA合成酶的识别都是至关重要的。最近的大肠杆菌遗传学研究表明，五个新基因tusABCDE的产物在（SU）-U-2修饰中起作用。在这里，我们解决了2.15埃晶体结构的E。coli TusBCD复合物，硫转移介体，形成由异源三聚体的二聚体组成的异源六聚体。基于结构的序列比对建议两个推定的活性位点Cys残基，Cys 79（在TusC中）和Cys 78（在TusD中），它们暴露在六聚体复合物上。体内突变体分析表明，只有Cys 78，在TusD亚基，参与硫转移过程中的s（2）U修饰过程。由于单个半胱氨酸作为催化残基，我们提出，TusBCD介导硫中继通过推定的过硫化物状态的TusD亚基。
Uridine at wobble position 34 of tRNA(Lys), tRNA(Glu), and tRNA Gin is exclusively modified into 2-thiouridine (s(2)U), which is crucial for both precise codon recognition and recognition by the cognate aminoacyl-tRNA synthetases. Recent Escherichia coli genetic studies revealed that the products of five novel genes, tusABCDE, function in the (SU)-U-2 modification. Here, we solved the 2.15 angstrom crystal structure of the E. coli TusBCD complex, a sulfur transfer mediator, forming a heterohexamer composed of a dimer of the hetero-trimer. Structure-based sequence alignment suggested two putative active site Cys residues, Cys79 (in TusC) and Cys78 (in TusD), which are exposed on the hexameric complex. In vivo mutant analyses revealed that only Cys78, in the TusD subunit, participates in sulfur transfer during the s(2)U modification process. Since the single Cys acts as a catalytic residue, we proposed that TusBCD mediates sulfur relay via a putative persulfide state of the TusD subunit.