Andersson S G, Buckingham R H, Kurland C G
EMBO J. 1984 Jan;3(1):91-4. doi: 10.1002/j.1460-2075.1984.tb01766.x.
Escherichia coli ribosomes pre-initiated with N-acetyl-Val-tRNAVal elongate strictly alternating poly(U-G) at a rate between eight and 12 peptide bonds per second per ribosome in vitro. Comparisons with poly(U)-primed poly(Phe) synthesis show that these systems function with the same rates which are close to those of protein synthesis in vivo. This indicates that, at least in vitro, codon composition has no marked influence on the speed of elongation when the concentration of ternary complex is saturating. Furthermore, the missense frequencies for the two polymers are within the same range: the missense substitution of Trp for Cys is 10(-4) and that of Met for Val is 10(-3) in the poly(U-G)-primed system. These data argue against models that explain the codon preference of certain gene families by postulating effects of high or low GC content of codons on the performance characteristics of ribosomes.
用N - 乙酰 - 缬氨酰 - tRNAVal预起始的大肠杆菌核糖体，在体外以每个核糖体每秒8至12个肽键的速率严格交替延伸聚（U - G）。与聚（U）引发的聚（苯丙氨酸）合成的比较表明，这些系统以与体内蛋白质合成相近的相同速率发挥作用。这表明，至少在体外，当三元复合物浓度饱和时，密码子组成对延伸速度没有显著影响。此外，两种聚合物的错义频率在同一范围内：在聚（U - G）引发的系统中，色氨酸错义取代半胱氨酸的频率为10^(-4)，甲硫氨酸错义取代缬氨酸的频率为10^(-3)。这些数据与通过假设密码子的高或低GC含量对核糖体性能特征的影响来解释某些基因家族密码子偏好的模型相悖。
