Hazkani-Covo Einat, Altman Neta, Horowitz Mia, Graur Dan
Department of Zoology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Ramat Aviv 69978, Israel.
J Mol Evol. 2002 Jan;54(1):30-4. doi: 10.1007/s00239-001-0014-0.
Prosaposin is a multifunctional protein encoded by a single-copy gene. It contains four saposin domains (A, B, C, and D) occurring as tandem repeats connected by linker sequences. Because the saposin domains are similar to one another, it is deduced that they were created by sequential duplications of an ancestral domain. There are two types of evolutionary scenarios that may explain the creation of the four-domain gene: (1) two rounds of tandem internal gene duplication and (2) three rounds of duplications. An evolutionary and phylogenetic analysis of saposin DNA and amino acid sequences from human, mouse, rat, chicken, and zebrafish indicates that the first evolutionary scenario is the most likely. Accordingly, an ancestral saposin-unit duplication produced a two-domain gene, which, subsequently, underwent a second complete tandem duplication to give rise to the present four-domain structure of the prosaposin gene.
鞘脂激活蛋白原是一种由单拷贝基因编码的多功能蛋白质。它包含四个鞘脂激活蛋白结构域（A、B、C和D），这些结构域以串联重复的形式存在，由连接序列相连。由于鞘脂激活蛋白结构域彼此相似，推测它们是由一个祖先结构域的连续重复产生的。有两种进化情形可以解释四结构域基因的产生：（1）两轮串联内部基因重复；（2）三轮重复。对来自人类、小鼠、大鼠、鸡和斑马鱼的鞘脂激活蛋白DNA和氨基酸序列进行的进化和系统发育分析表明，第一种进化情形是最有可能的。因此，一个祖先鞘脂激活蛋白单元的重复产生了一个双结构域基因，随后，该基因经历了第二次完整的串联重复，从而产生了目前鞘脂激活蛋白原基因的四结构域结构。
