载脂蛋白多基因家族分子进化的研究

与脂质运输有关的载脂蛋白基因构成一个复杂的多基因家族。为探讨这种演化时间长的基因家族的进化规律，本文首先建立了一种在非均衡进化速率条件下计算系统发生树中任意分支长度的简易方法，并可在此基础上算出无根分支系统树中分歧年代的期望值。进一步对本文科１０个种属共２６种载脂蛋白的系统演作作了实际分析，结果提示：①ＡｐｏＡ－Ｉ＇ＡｐｏＡ－ＩＶ，ＡｐｏＥ及ＡｐｏＡ－ＩＩ的共同祖先可能在奥陶纪水生脊椎动物中就已存

Studies on the Molecular Evolution of Apilipoprotein Multigene Family

The apolipoprotein genes represent a large family of genes encoding various binding proteins for plasma lipid transport.Because of their long divergence history,it is not known whether and how these genes have evolved through gene duplication from a common ancestor. To test this possibility and reconstruct a reliable phylogenetic tree,a simple method to evaluate the branch length and its divergence time in unrooted parsimony tree under the condition of non-even evolutionary rate was developed.The tree built from the 26 apolipoprotein sequences by above method clearly shows:(1) The common ancestor of ApoA-I ApoA-II,ApoA-IV,ApoE may appear 460 million years ago in an ordovician vertebrate which may be related with the major apolipoprotein LAL 1 and LAL2 in Lamprey from the evidence of sequence alignment;(2) The central role of different selection pressure upon the ancestor gene of apolipoprotein made them evolved into different subgroups,(3) The high evoluion rate in rodent ApoE molecules may be related with the existence of a large amount of hidden substitutions and the disruption of synonym codon usage clock in their genome;(4)The evolutionary rate of various branches in parsimony tree is significantly different in which the average UEP of ApoA-I,ApoA-IV is 2.0 MY,ApoA-II 1.7MY,ApoE 2.4MY;(5) The receptor domain in ApoE seems to be more conservative than other fragments.These data suggest a long,complex evolutionary history for apolipoprotein genes in which the gene duplication events of different origins took place.