Melançon P, Tapprich W E, Brakier-Gingras L
Département de Biochimie, Université de Montréal, Canada.
J Bacteriol. 1992 Dec;174(24):7896-901. doi: 10.1128/jb.174.24.7896-7901.1992.
Two single-base substitutions were constructed in the 2660 loop of Escherichia coli 23S rRNA (G2661-->C or U) and were introduced into the rrnB operon cloned in plasmid pKK3535. Ribosomes were isolated from bacteria transformed with the mutated plasmids and assayed in vitro in a poly(U)-directed system for their response to the misreading effect of streptomycin, neomycin, and gentamicin, three aminoglycoside antibiotics known to impair the proofreading control of translational accuracy. Both mutations decreased the stimulation of misreading by these drugs, but neither interfered with their binding to the ribosome. The response of the mutant ribosomes to these drugs suggests that the 2660 loop, which belongs to the elongation factor Tu binding site, is involved in the proofreading step of the accuracy control. In vivo, both mutations reduced read-through of nonsense codons and frameshifting, which can also be related to the increased efficiency in proofreading control which they confer to ribosomes.
在大肠杆菌23S rRNA的2660环中构建了两个单碱基替换（G2661→C或U），并将其引入克隆于质粒pKK3535的rrnB操纵子中。从用突变质粒转化的细菌中分离核糖体，并在聚（U）指导的系统中进行体外测定，以检测它们对链霉素、新霉素和庆大霉素这三种氨基糖苷类抗生素错读效应的反应，这三种抗生素已知会损害翻译准确性的校对控制。两种突变都降低了这些药物对错读的刺激，但都不影响它们与核糖体的结合。突变核糖体对这些药物的反应表明，属于延伸因子Tu结合位点的2660环参与了准确性控制的校对步骤。在体内，两种突变都减少了无义密码子的通读和移码，这也可能与它们赋予核糖体的校对控制效率提高有关。
