Compensatory evolution reveals functional interactions between ribosomal proteins S12 L14 and L19
Compensatory evolution reveals functional interactions between ribosomal proteins S12 L14 and L19
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DOI：
10.1016/j.jmb.2006.11.047
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发表时间：
2007-02-09
影响因子：
5.6
通讯作者：
Andersson, Dan I.
中科院分区：
文献类型：
--
作者：
Maisnier-Patin, Sophie;Paulander, Wilhelm;Andersson, Dan I.
S12是一种与翻译延伸率和翻译准确性有关的核糖体蛋白质，S12中的某些突变赋予对氨基糖苷类链霉素的抗性。先前我们在鼠伤寒沙门氏菌中表明，由于S12中的氨基酸取代K42N而导致的适应性成本，即生长速率降低，可以通过位于核糖体蛋白S4，S5和L19中的至少35种不同突变来补偿。在这里，我们已经在体内的健身，翻译速度和翻译准确性的四个不同的L19突变体的特点。当与位于S12的抗性突变分开时，L19中40位的三个不同的补偿性氨基酸取代（Q40H、Q40L和Q40R）引起适合度降低，而G104A变化对细菌生长没有影响。蛋白质合成速率不受位置40处突变的影响或增加，并且UGA无义密码子的通读水平在体内增加，表明翻译准确性的损失。L19中的突变增加了对在A位点有活性的氨基糖苷类的敏感性，进一步表明了解码步骤的扰动。这些表型与经典的S4和S5 ram（核糖体模糊性）突变体的表型相似。通过连续传代进化低适应性L19突变体，我们表明L19突变所带来的适应性成本可以通过核糖体蛋白L19本身、S12和L14（一种位于L19附近的蛋白质）中的额外突变来补偿。我们的研究结果揭示了一种新的功能作用，50 S核糖体蛋白L19在蛋白质合成过程中，支持已发表的结构数据表明，L14和L19与16 S rRNA的相互作用可能会影响30 S亚基的功能。此外，我们的研究表明，补偿适应性进化可以用来发现新的核糖体蛋白质的分子功能。(c)2006爱思唯尔有限公司保留所有权利。
Certain mutations in S12, a ribosomal protein involved in translation elongation rate and translation accuracy, confer resistance to the arninoglycoside streptomycin. Previously we showed in Salmonella typhimurium that the fitness cost, i.e. reduced growth rate, due to the amino acid substitution K42N in S12 could be compensated by at least 35 different mutations located in the ribosomal proteins S4, S5 and L19. Here, we have characterized in vivo the fitness, translation speed and translation accuracy of four different L19 mutants. When separated from the resistance mutation located in S12, the three different compensatory amino acid substitutions in L19 at position 40 (Q40H, Q40L and Q40R) caused a decrease in fitness while the G104A change had no effect on bacterial growth. The rate of protein synthesis was unaffected or increased by the mutations at position 40 and the level of readthrough of a UGA nonsense codon was increased in vivo, indicating a loss of translational accuracy. The mutations in L19 increased sensitivity to aminoglycosides active at the A-site, further indicating a perturbation of the decoding step. These phenotypes are similar to those of the classical S4 and S5 ram (ribosomal ambiguity) mutants. By evolving low-fitness L19 mutants by serial passage, we showed that the fitness cost conferred by the L19 mutations could be compensated by additional mutations in the ribosomal protein L19 itself, in S12 and in L14, a protein located close to L19. Our results reveal a novel functional role for the 50 S ribosomal protein L19 during protein synthesis, supporting published structural data suggesting that the interaction of L14 and L19 with 16 S rRNA could influence function of the 30 S subunit. Moreover, our study demonstrates how compensatory fitness-evolution can be used to discover new molecular functions of ribosomal proteins. (c) 2006 Elsevier Ltd. All rights reserved.