Mangat Chand S, Brown Eric D
Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario, L8S 3Z5, Canada.
Mol Microbiol. 2008 Dec;70(5):1051-3. doi: 10.1111/j.1365-2958.2008.06484.x.
Many trans-acting factors that aid in ribosome biogenesis have been identified in higher organisms but relatively few such factors are known in prokaryotes. In bacteria, the list of such factors includes ATP-energized helicases and chaperones as well as an emerging cadre of switch GTPases. The KsgA protein is a universally conserved methyltransferase that dimethylates both A1518 and A1519 of the 16S rRNA of the small ribosomal subunit. Methylation has long been thought to be solely for fine-tuning of protein translation. In this issue of Molecular Microbiology, Connolly et al. present data suggesting KsgA might function in the assembly of the small subunit of the ribosome. Indeed, the work indicates that KsgA might have a checkpoint role in ribosome biogenesis where methylation by this protein marks the completion of its assembly role. These findings open our thinking to new candidate assembly factors and provide a new direction for understanding ribosome assembly.
在高等生物中，许多有助于核糖体生物合成的反式作用因子已被鉴定出来，但在原核生物中，这类因子相对较少。在细菌中，这类因子包括ATP供能解旋酶、分子伴侣以及新兴的开关GTP酶。KsgA蛋白是一种普遍保守的甲基转移酶，它能使小核糖体亚基16S rRNA的A1518和A1519位点发生二甲基化。长期以来，甲基化一直被认为仅仅是用于微调蛋白质翻译。在本期《分子微生物学》中，康诺利等人发表的数据表明，KsgA可能在核糖体小亚基的组装中发挥作用。事实上，这项研究表明，KsgA可能在核糖体生物合成中具有一个检查点作用，即该蛋白的甲基化标志着其组装作用的完成。这些发现为我们开拓了对新的候选组装因子的思路，并为理解核糖体组装提供了新的方向。
