2012年11月7日 訊 /生物谷BIOON/ --近日,，來自西班牙國家基因組研究中心的研究者研究發(fā)現(xiàn)了，在不同物種中,，大多數(shù)的氨基酸替代物都存在不同的適應(yīng)性,，這是一項重要的研究發(fā)現(xiàn)，揭示了機體中氨基酸是否被修飾的一個新的證據(jù),，這種修飾是在蛋白質(zhì)水平上調(diào)節(jié)分子進化的主要因素,。相關(guān)研究成果刊登于國際雜志Ntuare上。
這項研究中,，研究者分析了大量的實驗數(shù)據(jù)來揭示不同類型的基因是如何產(chǎn)生的,，研究者Fyodor Kondrashov表示，在此前的研究中,，他們發(fā)現(xiàn)了有機體中的某些引發(fā)疾病的突變或許在別的有機體中是無害的,。
很多科學(xué)家假設(shè)，在較短時間內(nèi),，機體中同一個基因的兩個相同的拷貝不會對機體有任何影響,，但是研究者Fyodor Kondrashov指出，如此的復(fù)制很有可能使得機體處于有害狀態(tài)或者有益的狀態(tài),，我們的研究結(jié)果證實了這一點,。決定分子進化的速度和模式的因素始終處于進化生物學(xué)的最前端研究中。許多研究重點關(guān)注了選擇性遺傳漂變在氨基酸替代物上的作用,，科學(xué)家們目前確定,，自然選擇或遺傳突變都會促成進化過程中的一項重要事件,。
這項研究并不最新領(lǐng)域的研究了，早在20世紀已經(jīng)有人開始了相關(guān)研究,。然而分子進化僅僅在20世紀60年代才開始,，在20世紀70年代以后，核酸測序使得分子進化相關(guān)研究進入了更深的一個層面,。（生物谷Bioon.com）
編譯自：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.
