Haefliger D N, Moskaitis J E, Schoenberg D R, Wahli W
Institut de Biologie animale, Université de Lausanne, Switzerland.
J Mol Evol. 1989 Oct;29(4):344-54. doi: 10.1007/BF02103621.
The Xenopus laevis 68-kd and 74-kd albumin amino acid sequences are examined with respect to their relationship to the other known members of the albumin/alpha-fetoprotein/vitamin D-binding protein gene family. Each of the three members of this family presents a unique pattern of conserved regions indicating a differential selective pressure related to specific functional characteristics. Furthermore, an evolutionary tree of these genes was deduced from the divergence times calculated from direct nucleotide sequence comparisons of individual gene pairs. These calculations indicate that the vitamin D-binding protein/albumin separation occurred 560-600 million years (Myr) ago and the albumin/alpha-fetoprotein divergence 280 Myr ago. This observation leads to the hypothesis according to which the albumin/alpha-fetoprotein gene duplication occurred shortly after the amphibian/reptile separation. Consequently, and unlike mammals, amphibians and fishes should lack an alpha-fetoprotein in their serum at larval stages, which is consistent with a recent analysis of serum proteins in Xenopus laevis larvae. This hypothesis now will have to be tested further in additional lower vertebrates.
研究了非洲爪蟾68kd和74kd白蛋白的氨基酸序列与白蛋白/甲胎蛋白/维生素D结合蛋白基因家族其他已知成员的关系。该家族的三个成员各自呈现出独特的保守区域模式，表明与特定功能特征相关的差异选择压力。此外，根据从单个基因对的直接核苷酸序列比较计算出的分歧时间，推导出了这些基因的进化树。这些计算表明，维生素D结合蛋白/白蛋白的分离发生在5.6亿至6亿年前，白蛋白/甲胎蛋白的分歧发生在2.8亿年前。这一观察结果引出了一个假说，即白蛋白/甲胎蛋白基因复制发生在两栖动物/爬行动物分离后不久。因此，与哺乳动物不同，两栖动物和鱼类在幼体阶段的血清中应该缺乏甲胎蛋白，这与最近对非洲爪蟾幼体血清蛋白的分析一致。现在必须在更多的低等脊椎动物中进一步验证这一假说。
