Structural basis for the function of a small GTPase RsgA on the 30S ribosomal subunit maturation revealed by cryoelectron microscopy
Structural basis for the function of a small GTPase RsgA on the 30S ribosomal subunit maturation revealed by cryoelectron microscopy
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冷冻电镜揭示小 GTPase RsgA 对 30S 核糖体亚基成熟功能的结构基础
DOI：
10.1073/pnas.1104645108
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发表时间：
2011-08-09
影响因子：
11.1
通讯作者：
Gao, Ning
中科院分区：
文献类型：
--
作者：
Guo, Qiang;Yuan, Yi;Gao, Ning
细菌RsgA是一种循环排列的GTP酶，其GTP酶活性依赖于30S核糖体亚基，是参与30S亚基成熟的晚期核糖体生物合成因子。 RsgA 的作用是以 GTP 依赖性方式从成熟的 30S 亚基中释放另一个 30S 生物合成因子 RbfA。使用冷冻电子显微镜，我们以亚纳米分辨率确定了在 GMPPNP 存在下与 RsgA 结合的 30S 亚基的结构。在结构中，RsgA与30S亚基的中央部分结合，靠近解码中心，其位置与多种生物发生因子、所有三个翻译起始因子以及A位点、P位点tRNA和50S亚基不相容。进一步的结构分析不仅为新生 30S 亚基中 RsgA 依赖性释放 RbfA 提供了结构模型，而且还表明了 RsgA 在核糖体蛋白组装中的作用，以促进某些三级结合蛋白的掺入。此外，结合现有的生化和遗传数据，我们的结果表明，RsgA可能是30S亚基生物发生后期的通用检查点蛋白，其功能不仅是从新生的30S亚基中释放生物发生因子（例如RbfA），而且还阻断起始因子与过早的30S亚基的关联。
The bacterial RsgA, a circularly permutated GTPase, whose GTPase activity is dependent on the 30S ribosomal subunit, is a late-stage ribosome biogenesis factor involved in the 30S subunit maturation. The role of RsgA is to release another 30S biogenesis factor, RbfA, from the mature 30S subunit in a GTP-dependent manner. Using cryoelectron microscopy, we have determined the structure of the 30S subunit bound with RsgA in the presence of GMPPNP at subnanometer resolution. In the structure, RsgA binds to the central part of the 30S subunit, close to the decoding center, in a position that is incompatible with multiple biogenesis factors, all three translation initiation factors, as well as A-, P-site tRNAs and the 50S subunit. Further structural analysis not only provides a structural model for the RsgA-dependent release of RbfA from the nascent 30S subunit, but also indicates RsgA’s role in the ribosomal protein assembly, to promote some tertiary binding protein incorporation. Moreover, together with available biochemical and genetic data, our results suggest that RsgA might be a general checkpoint protein in the late stage of the 30S subunit biogenesis, whose function is not only to release biogenesis factors (e.g., RbfA) from the nascent 30S subunit, but also to block the association of initiation factors to the premature 30S subunit.