Fares Mario Ali, Barrio Eladio, Sabater-Muñoz Beatriz, Moya Andrés
Institut "Cavanilles" de Biodiversitat i Biologia Evolutiva and Department de Genètica, Universitat de València, Spain.
Mol Biol Evol. 2002 Jul;19(7):1162-70. doi: 10.1093/oxfordjournals.molbev.a004174.
The heat-shock protein GroEL is a double-ring-structured chaperonin that assists the folding of many newly synthesized proteins in Escherichia coli and the refolding in vitro, with the cochaperonin GroES, of conformationally damaged proteins. This protein is constitutively overexpressed in the primary symbiotic bacteria of many insects, constituting approximately 10% of the total protein in Buchnera, the primary endosymbiont of aphids. In the present study, we perform a maximum likelihood (ML) analysis to unveil the selective constraints in GroEL. In addition, we apply a new statistical approach to determine the patterns of evolution in this highly interesting protein. The main conclusion derived from our analysis is that GroEL has suffered an accelerated rate of amino acid substitution upon the symbiotic integration of Buchnera into the aphids. It is most interesting that the ML analysis of codon substitutions in the different branches of the phylogenetic tree strongly supports the action of positive selection in the different lineages of BUCHNERA: Additionally, the new sliding window analysis of the complete groEL sequence reveals different regions of the molecule under the action of positive selection, mainly located in the apical domain, that are important for both peptide and GroES binding.
热休克蛋白GroEL是一种双环结构的伴侣蛋白，在大肠杆菌中协助许多新合成蛋白质的折叠，并在体外与伴侣蛋白GroES一起协助构象受损蛋白质的重折叠。这种蛋白质在许多昆虫的初级共生细菌中组成性过表达，在蚜虫的主要内共生体布赫纳氏菌中约占总蛋白的10%。在本研究中，我们进行了最大似然（ML）分析以揭示GroEL中的选择性限制。此外，我们应用一种新的统计方法来确定这种高度有趣蛋白质的进化模式。我们分析得出的主要结论是，在布赫纳氏菌共生整合到蚜虫体内后，GroEL的氨基酸替代速率加快。最有趣的是，系统发育树不同分支中密码子替代的ML分析有力地支持了布赫纳氏菌不同谱系中正向选择的作用：此外，对完整groEL序列的新滑动窗口分析揭示了分子中在正向选择作用下的不同区域，主要位于顶端结构域，这些区域对肽和GroES结合都很重要。
