Role of translational fidelity in cellular physiology of oral streptococci

摘要 核糖体由核糖核蛋白组成，是蛋白质生物合成所必需的，蛋白质生物合成是蛋白质生物合成的重要组成部分。 细胞中最复杂的生物过程。在原核生物中，成熟的核糖体含有蛋白质（r- 蛋白质）和RNA（rRNA）组装成成熟的70 S核糖体。70 S核糖体是由 由两个亚基组成，称为30 S（小）和50 S核糖体（大）亚基。小亚基是 由16 S核糖体RNA（rRNA）和20多个核心r-蛋白组成，而大亚基由 23 S和5S rRNA，以及30多种核心r蛋白。核糖体不是一个静止的实体， 适应不断变化的环境，从而产生核糖体异质性。此外，一些小 辅助蛋白调节核糖体的生物发生、再循环和功能;这些蛋白中的许多 它们的分子功能仍有待发现。 在蛋白质合成过程中，翻译保真度以高精度保持。但平均 与转录或复制错误相比，翻译错误率相对较高（每个密码子10-4至10-3 rates.维持适当的翻译保真度需要氨基酸和tRNA的同源配对， 氨酰-tRNA（aa-tRNA）合成酶和mRNA密码子的准确解码相应的aa- 核糖体上的tRNA几个核心和辅助r蛋白驱动密码子的正确解码， 保持翻译的保真度。各种应激条件如营养和氧化应激通常 导致错误翻译和细菌生长缺陷。我们最近确定了几个因素，包括 在变形链球菌（一种口腔病原体）中保守的新蛋白SprV（90个氨基酸）， 用于翻译保真度、压力耐受和适应。本研究的主要目的是了解 在分子水平上，SprV和其他辅助蛋白如L9（r-蛋白）和EF-P如何调节 翻译保真度以改变口腔链球菌的生理学和生物学适应性。

ABSTRACT Ribosomes are composed of ribonucleoproteins and are essential for protein biosynthesis, which is one of the most complex biological processes in the cell. In prokaryotes, mature ribosomes contain proteins (r- proteins) and RNA (rRNA) that are assembled into the mature 70S ribosome. The 70S ribosomes are made by two subunits, designated as the 30S (small) and the 50S ribosome (large) subunits. The small subunit is composed of the 16S ribosomal RNA (rRNA) and over 20 core r-proteins while the large subunit is composed of 23S and 5S rRNAs, and more than 30 core r-proteins. Ribosome is not a stationary entity, rather it is adapted to changing environments giving rise to ribosome heterogeneity. Additionally, several small accessory proteins modulate the biogenesis, recycling, and function of the ribosome; many of these proteins and their molecular functions remain to be discovered. During protein synthesis, translational fidelity is maintained with high accuracy. However, the average translation error rate is relatively higher (10-4 to 10-3 per codon) compared to transcription or replication error rates. Maintaining proper translational fidelity requires cognate pairing of amino acids and tRNAs by aminoacyl-tRNA (aa-tRNA) synthetase and accurate decoding of mRNA codons by the corresponding aa- tRNAs on the ribosome. Several core and accessory r-proteins drive the correct decoding of the codons to maintain the translational fidelity. Various stress conditions such as nutritional and oxidative stresses often lead to mistranslation and growth defects in bacteria. We have recently identified several factors including a conserved novel protein, SprV (90 amino acids), in Streptococcus mutans (an oral pathogen) that is required for translational fidelity, stress tolerance and adaptation. The major goal of this study is to understand at the molecular level how SprV and other accessory proteins such as L9 (r-protein) and EF-P modulate translational fidelity to alter physiology and biological fitness of oral streptococci.