Unité d'Ecologie Systématique et Evolution, CNRS UMR 8079, Université Paris-Sud, 91405 Orsay Cedex, France.
Archaea. 2012;2012:630910. doi: 10.1155/2012/630910. Epub 2012 Dec 16.
Archaea have idiosyncratic cell membranes usually based on phospholipids containing glycerol-1-phosphate linked by ether bonds to isoprenoid lateral chains. Since these phospholipids strongly differ from those of bacteria and eukaryotes, the origin of the archaeal membranes (and by extension, of all cellular membranes) was enigmatic and called for accurate evolutionary studies. In this paper we review some recent phylogenomic studies that have revealed a modified mevalonate pathway for the synthesis of isoprenoid precursors in archaea and suggested that this domain uses an atypical pathway of synthesis of fatty acids devoid of any acyl carrier protein, which is essential for this activity in bacteria and eukaryotes. In addition, we show new or updated phylogenetic analyses of enzymes likely responsible for the isoprenoid chain synthesis from their precursors and the phospholipid synthesis from glycerol phosphate, isoprenoids, and polar head groups. These results support that most of these enzymes can be traced back to the last archaeal common ancestor and, in many cases, even to the last common ancestor of all living organisms.
古菌具有独特的细胞膜，通常基于甘油-1-磷酸连接的醚键连接到异戊二烯侧链的磷脂。由于这些磷脂与细菌和真核生物的磷脂有很大的不同，因此古菌膜的起源（以及所有细胞膜的起源）是神秘的，需要进行准确的进化研究。在本文中，我们回顾了一些最近的基因组学研究，这些研究揭示了古菌中合成异戊二烯前体的改良甲羟戊酸途径，并表明该结构域使用了一种没有酰基辅酶 A 的典型脂肪酸合成途径，而酰基辅酶 A 对于细菌和真核生物的这种活性是必不可少的。此外，我们展示了新的或更新的酶的系统发育分析，这些酶可能负责从其前体合成异戊二烯链以及从甘油磷酸、异戊二烯和极性头基团合成磷脂。这些结果表明，这些酶中的大多数可以追溯到最后一个古菌共同祖先，在许多情况下，甚至可以追溯到所有生物的最后共同祖先。
