2012年11月7日 讯 /生物谷BIOON/ --近日，来自西班牙国家基因组研究中心的研究者研究发现了，在不同物种中，大多数的氨基酸替代物都存在不同的适应性，这是一项重要的研究发现，揭示了机体中氨基酸是否被修饰的一个新的证据，这种修饰是在蛋白质水平上调节分子进化的主要因素。相关研究成果刊登于国际杂志Ntuare上。
这项研究中，研究者分析了大量的实验数据来揭示不同类型的基因是如何产生的，研究者Fyodor Kondrashov表示，在此前的研究中，他们发现了有机体中的某些引发疾病的突变或许在别的有机体中是无害的。
很多科学家假设，在较短时间内，机体中同一个基因的两个相同的拷贝不会对机体有任何影响，但是研究者Fyodor Kondrashov指出，如此的复制很有可能使得机体处于有害状态或者有益的状态，我们的研究结果证实了这一点。决定分子进化的速度和模式的因素始终处于进化生物学的最前端研究中。许多研究重点关注了选择性遗传漂变在氨基酸替代物上的作用，科学家们目前确定，自然选择或遗传突变都会促成进化过程中的一项重要事件。
这项研究并不最新领域的研究了，早在20世纪已经有人开始了相关研究。然而分子进化仅仅在20世纪60年代才开始，在20世纪70年代以后，核酸测序使得分子进化相关研究进入了更深的一个层面。（生物谷Bioon.com）
编译自：The genetics of molecular evolution
doi:10.1038/nature11510
PMC:
PMID:
Epistasis as the primary factor in molecular evolution
Michael S. Breen, Carsten Kemena, Peter K. Vlasov, Cedric Notredame & Fyodor A. Kondrashov
The main forces directing long-term molecular evolution remain obscure. A sizable fraction of amino-acid substitutions seem to be fixed by positive selection1, 2, 3, 4, but it is unclear to what degree long-term protein evolution is constrained by epistasis, that is, instances when substitutions that are accepted in one genotype are deleterious in another. Here we obtain a quantitative estimate of the prevalence of epistasis in long-term protein evolution by relating data on amino-acid usage in 14 organelle proteins and 2 nuclear-encoded proteins to their rates of short-term evolution. We studied multiple alignments of at least 1,000 orthologues for each of these 16 proteins from species from a diverse phylogenetic background and found that an average site contained approximately eight different amino acids. Thus, without epistasis an average site should accept two-fifths of all possible amino acids, and the average rate of amino-acid substitutions should therefore be about three-fifths lower than the rate of neutral evolution. However, we found that the measured rate of amino-acid substitution in recent evolution is 20 times lower than the rate of neutral evolution and an order of magnitude lower than that expected in the absence of epistasis. These data indicate that epistasis is pervasive throughout protein evolution: about 90 per cent of all amino-acid substitutions have a neutral or beneficial impact only in the genetic backgrounds in which they occur, and must therefore be deleterious in a different background of other species. Our findings show that most amino-acid substitutions have different fitness effects in different species and that epistasis provides the primary conceptual framework to describe the tempo and mode of long-term protein evolution.
