Ribosomes of Archaea and Eukarya share higher homology with each other than with bacterial ribosomes. For example, there is a set of 35 r-proteins that are specific only for archaeal and eukaryotic ribosomes. Three of these proteins-eL19, eL24, and eL41-participate in interactions between ribosomal subunits. The eukaryote-specific extensions of r-proteins eL19 and eL24 form two intersubunit bridges eB12 and eB13, which are present only in eukaryotic ribosomes. The third r-protein, eL41, forms bridge eB14. Notably, eL41 is found in all eukaryotes but only in some Archaea. It has been shown that bridges eB12 and eB13 are needed for efficient translation, while r-protein eL41 plays a minor role in ribosome function. Here, the functional interactions between intersubunit bridges were studied using budding yeast strains lacking different combinations of the abovementioned bridges/proteins. The growth phenotypes, levels of in vivo translation, ribosome-polysome profiles, and in vitro association of ribosomal subunits were analyzed. The results show a genetic interaction between r-protein eL41 and the eB12 bridge-forming region of eL19, and between r-proteins eL41 and eL24. It was possible to construct viable yeast strains with Archaea-like ribosomes lacking two or three eukaryote-specific bridges. These strains display slow growth and a poor translation phenotype. In addition, bridges eB12 and eB13 appear to cooperate during ribosome subunit association. These results indicate that nonessential structural elements of r-proteins become highly important in the context of disturbed subunit interactions. Therefore, eukaryote-specific bridges may contribute to the evolutionary success of eukaryotic translation machinery.

中文翻译：

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酿酒酵母核糖体亚基间桥的功能相互作用。


古细菌和真核生物的核糖体彼此之间比细菌核糖体具有更高的同源性。例如，有一组 35 种 r 蛋白，仅对古菌和真核核糖体具有特异性。其中三种蛋白质（eL19、eL24 和 eL41）参与核糖体亚基之间的相互作用。 r 蛋白 eL19 和 eL24 的真核生物特异性延伸形成两个亚基间桥 eB12 和 eB13，仅存在于真核生物核糖体中。第三个 r 蛋白 eL41 形成桥 eB14。值得注意的是，eL41 存在于所有真核生物中，但仅存在于某些古细菌中。研究表明，有效翻译需要桥 eB12 和 eB13，而 r 蛋白 eL41 在核糖体功能中起次要作用。在这里，使用缺乏上述桥/蛋白质的不同组合的出芽酵母菌株研究了亚基间桥之间的功能相互作用。分析了生长表型、体内翻译水平、核糖体-多核糖体谱和核糖体亚基的体外关联。结果显示 r 蛋白 eL41 和 eL19 的 eB12 桥形成区域之间以及 r 蛋白 eL41 和 eL24 之间存在遗传相互作用。有可能构建具有缺乏两个或三个真核生物特异性桥的古细菌样核糖体的可行酵母菌株。这些菌株表现出生长缓慢和翻译表型较差。此外，桥 eB12 和 eB13 似乎在核糖体亚基缔合过程中进行合作。这些结果表明，r 蛋白的非必需结构元件在亚基相互作用受到干扰的情况下变得非常重要。因此，真核生物特异性的桥可能有助于真核翻译机器的进化成功。