Functional interaction between ribosomal protein L6 and RbgA during ribosome assembly.
Functional interaction between ribosomal protein L6 and RbgA during ribosome assembly.
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DOI：
10.1371/journal.pgen.1004694
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发表时间：
2014-10
期刊：
影响因子：
4.5
通讯作者：
Britton RA
中科院分区：
文献类型：
--
作者：
Gulati M;Jain N;Davis JH;Williamson JR;Britton RA
RBGA是一个必不可少的GTPase，它参与枯草芽孢杆菌中大型核糖体亚基的组装及其同源物与线粒体和真核大型亚基组装有关。 RBGA在此过程中的功能仍然很少了解。为了深入了解RBGA的功能，我们分离了抑制突变，这些突变部分恢复了造成严重生长缺陷的RBGA突变（RBGA-F6A）的生长。对这些抑制剂的分析在RPLF中鉴定出突变，编码核糖体蛋白L6。抑制剂菌株均积累了一种新型的核糖体中间体，该中间体在蔗糖梯度中以44S迁移。所有突变簇簇在L6区域，该区域与23S rRNA的螺旋97密切接触。体外成熟测定表明，L6取代允许有缺陷的RBGA-F6A蛋白在核糖体成熟中更有效地发挥作用。我们的结果表明，在掺入L16和其他晚期组装蛋白之前，RBGA的功能可以在核糖体上正确定位L6。
核糖体是复杂的大分子机器，它们在细胞中执行蛋白质合成的基本功能。核糖体亚基的组装是一个多步过程，涉及3个rRNA分子和> 50核糖体蛋白的准确和及时组装。近年来，在细菌和真核细胞中已经确定了许多核糖体组装因子。但是，它们在核糖体生物发生中的精确功能知之甚少。我们先前已经表明，GTPase RBGA是从细菌到人保守的蛋白质，对于枯草芽孢杆菌中的核糖体组装至关重要。在这里，我们表明，由RBGA突变引起的生长缺陷被核糖体蛋白L6突变所部分抑制。抑制剂菌株积累了新型的核糖体中间体，这些中间体似乎通过削弱核糖体L6相互作用并促进RBGA依赖性组件来抑制RBGA缺陷。我们的工作为组装过程中核糖体组装因子RBGA与核糖体蛋白L6之间的功能相互作用提供了证据，这对于线粒体，叶绿体和真核核糖体组装也可能很重要。
RbgA is an essential GTPase that participates in the assembly of the large ribosomal subunit in Bacillus subtilis and its homologs are implicated in mitochondrial and eukaryotic large subunit assembly. How RbgA functions in this process is still poorly understood. To gain insight into the function of RbgA we isolated suppressor mutations that partially restored the growth of an RbgA mutation (RbgA-F6A) that caused a severe growth defect. Analysis of these suppressors identified mutations in rplF, encoding ribosomal protein L6. The suppressor strains all accumulated a novel ribosome intermediate that migrates at 44S in sucrose gradients. All of the mutations cluster in a region of L6 that is in close contact with helix 97 of the 23S rRNA. In vitro maturation assays indicate that the L6 substitutions allow the defective RbgA-F6A protein to function more effectively in ribosome maturation. Our results suggest that RbgA functions to properly position L6 on the ribosome, prior to the incorporation of L16 and other late assembly proteins. Ribosomes are complex macromolecular machines that carry out the essential function of protein synthesis in the cell. The assembly of ribosomal subunits is a multistep process that involves the accurate and timely assembly of 3 rRNA molecules and>50 ribosomal-proteins. In recent years many ribosome assembly factors have been identified in bacterial and eukaryotic cells; however, their precise functions in ribosome biogenesis are poorly understood. We have previously shown that the GTPase RbgA, a protein conserved from bacteria to humans, is essential for ribosome assembly in Bacillus subtilis. Here, we show that growth defect caused by a mutation in RbgA is partially suppressed by mutations in ribosomal protein L6. The suppressor strains accumulate novel ribosomal intermediates that appear to suppress the RbgA defect by weakening the interaction of L6 for the ribosome and facilitating RbgA dependent assembly. Our work provides evidence for a functional interaction between ribosome assembly factor RbgA and ribosomal protein L6 during assembly, a function that is likely important for mitochondrial, chloroplast, and eukaryotic ribosome assembly as well.