Li S L, Denney R M, Yanofsky C
Proc Natl Acad Sci U S A. 1973 Apr;70(4):1112-6. doi: 10.1073/pnas.70.4.1112.
Two different estimates were obtained for the extent of nucleotide sequence divergence in the structural genes of the tryptophan synthetase alpha-chains of Escherichia coli, Salmonella typhimurium, and Aerobacter aerogenes. One estimate was based on comparisons of the amino acid sequences of the respective alpha chains. The other was derived from measurements of the thermal stability of RNA-DNA hybrids formed with phage DNA carrying the alpha-chain structural gene of E. coli and labeled messenger RNA from the three bacterial species. Comparison of the two estimates suggests that during the course of evolution synonymous codon changes have accumulated in the alpha-chain-structural genes.
对大肠杆菌、鼠伤寒沙门氏菌和气杆菌色氨酸合成酶α链结构基因中核苷酸序列差异的程度,获得了两种不同的估计值。一种估计是基于各自α链氨基酸序列的比较。另一种是通过测量由携带大肠杆菌α链结构基因的噬菌体DNA与来自这三种细菌的标记信使RNA形成的RNA-DNA杂种的热稳定性得出的。两种估计值的比较表明,在进化过程中,同义密码子变化已在α链结构基因中积累。