Knöchel W, Korge E, Basner A, Meyerhof W
J Mol Evol. 1986;23(3):211-23. doi: 10.1007/BF02115578.
Globin mRNAs of Xenopus borealis and Xenopus tropicalis have been cloned and sequenced. The nucleotide and derived amino acid sequences were compared with each other and with already available data from Xenopus laevis. This analysis rendered clear evidence that the common ancestor of X. laevis and X. borealis, but not of X. tropicalis, had lost one amino acid of the beta-globins prior to a genome duplication event that preceded the segregation of the former two species. Replacement-site substitutions were used to calculate a rough time scale of genome duplication and species segregation. The results suggest an ancient separation between the X. laevis and the X. tropicalis groups occurring approximately 110-120 million years ago. Analysis of the amino acid chains demonstrated various alterations. However, some functional domains, like heme-binding sites and alpha 1 beta 2 contact sites, were subject to a high degree of conservation, indicating the existence of functional constraints on them also in the genus Xenopus.
北方非洲爪蟾和热带非洲爪蟾的珠蛋白信使核糖核酸已被克隆并测序。将其核苷酸和推导的氨基酸序列相互比较，并与非洲爪蟾已有的数据进行比较。该分析提供了明确的证据，表明非洲爪蟾和北方非洲爪蟾的共同祖先，而非热带非洲爪蟾的共同祖先，在导致前两个物种分离的基因组复制事件之前就已丢失了β-珠蛋白的一个氨基酸。利用替换位点替换来计算基因组复制和物种分离的大致时间尺度。结果表明，非洲爪蟾和热带非洲爪蟾群体之间的古老分离大约发生在1.1亿至1.2亿年前。对氨基酸链的分析显示出各种变化。然而，一些功能域，如血红素结合位点和α1β2接触位点，高度保守，这表明在非洲爪蟾属中它们也存在功能限制。
