Bossi L
J Mol Biol. 1983 Feb 15;164(1):73-87. doi: 10.1016/0022-2836(83)90088-8.
The efficiency of various suppressor tRNAs in reading the UAG amber codon has been measured at 42 sites in the lacI gene. Results indicate that: (1) for all suppressors, efficiency is not an a priori value; rather, it is determined at each site by the specific reading context of the suppressed codon; (2) the degree of sensitivity to context effects differs among suppressors. Most affected is amber suppressor supE (su2), whose activity varies over a 20-fold range depending on context; (3) context effects are produced by residues present at the 3' side of the UAG codon. The most important role appears to be played by the base that is immediately adjacent to the codon. When this base is a purine, the amber codon is suppressed more efficiently than when a pyrimidine is in the same position. Superimposed on this initial pattern, the influence of bases further downstream to the UAG triplet can be detected also. The possibility is discussed that context effects are produced by the whole codon following UAG in the message.
已在乳糖抑制蛋白（lacI）基因的42个位点测定了各种抑制性tRNA读取UAG琥珀密码子的效率。结果表明：（1）对于所有抑制子而言，效率并非一个先验值；相反，它在每个位点由被抑制密码子的特定读取上下文决定；（2）抑制子对上下文效应的敏感程度各不相同。受影响最大的是琥珀抑制子supE（su2），其活性根据上下文在20倍的范围内变化；（3）上下文效应由UAG密码子3'侧的残基产生。紧邻密码子的碱基似乎起着最重要的作用。当该碱基为嘌呤时，琥珀密码子比嘧啶处于相同位置时更有效地被抑制。叠加在这种初始模式上，也可以检测到UAG三联体下游更远碱基的影响。文中讨论了这样一种可能性，即上下文效应是由信使中UAG之后的整个密码子产生的。
