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首页> 外文期刊>Journal of Molecular Biology >Structural rearrangements in the active site of the Thermus thermophilus 16S rRNA methyltransferase KsgA in a binary complex with 5'-methylthioadenosine.
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Structural rearrangements in the active site of the Thermus thermophilus 16S rRNA methyltransferase KsgA in a binary complex with 5'-methylthioadenosine.

机译：与5'-甲基硫代腺苷二元复合物中嗜热栖热菌16S rRNA甲基转移酶KsgA活性位点的结构重排。

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摘要

Posttranscriptional modification of ribosomal RNA (rRNA) occurs in all kingdoms of life. The S-adenosyl-L-methionine-dependent methyltransferase KsgA introduces the most highly conserved rRNA modification, the dimethylation of A1518 and A1519 of 16S rRNA. Loss of this dimethylation confers resistance to the antibiotic kasugamycin. Here, we report biochemical studies and high-resolution crystal structures of KsgA from Thermus thermophilus. Methylation of 30S ribosomal subunits by T. thermophilus KsgA is more efficient at low concentrations of magnesium ions, suggesting that partially unfolded RNA is the preferred substrate. The overall structure is similar to that of other methyltransferases but contains an additional alpha-helix in a novel N-terminal extension. Comparison of the apoenzyme with complex structures with 5'-methylthioadenosine or adenosine bound in the cofactor-binding site reveals novel features when compared with related enzymes. Several mobile loop regions that restrict access to the cofactor-binding site are observed. In addition, the orientation of residues in the substrate-binding site indicates that conformational changes are required for binding two adjacent residues of the substrate rRNA.
机译：核糖体RNA（rRNA）的转录后修饰发生在所有生命王国中。 S-腺苷-L-蛋氨酸依赖性甲基转移酶KsgA引入了最高度保守的rRNA修饰，即16S rRNA的A1518和A1519的二甲基化。这种二甲基化的丧失赋予了对抗生素春日霉素的抗性。在这里，我们报道了嗜热栖热菌的KsgA的生化研究和高分辨率晶体结构。在低浓度的镁离子下，嗜热链球菌KsgA对30S核糖体亚基的甲基化效率更高，这表明部分展开的RNA是优选的底物。总体结构类似于其他甲基转移酶，但在新的N端延伸区中包含一个额外的α-螺旋。与辅酶结合位点上结合有5'-甲硫基腺苷或腺苷的复杂结构的脱辅基酶相比，与相关酶相比，具有新颖的功能。观察到几个限制进入辅因子结合位点的移动环区域。另外，底物结合位点中残基的方向表明结合底物rRNA的两个相邻残基需要构象变化。

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