Evolution, Structure, and Function of Leucine rich Repeats as Revealed by Bioinformatics

富含亮氨酸重复序列(LRR)存在于从病毒到真核生物的20,000多种蛋白质中。两到六十二个LRR同时发生。大多数LRR蛋白参与蛋白质、配体和蛋白质、蛋白质之间的相互作用，包括植物免疫反应和哺乳动物的先天免疫反应。每个含有20-30个残基的重复序列可分为一个高度保守的片段和一个可变片段。植物特异性LRRs(类：PS-LRR)以前只在植物蛋白中被识别。然而，我们发现PS-LRRs也存在于11个细菌物种的20个蛋白质中。我们指出，编码PS-LRR结构域的基因/基因片段在细菌和植物之间发生了水平的基因转移，而不是共同祖先的后代。此外，我们还发现了到目前为止还未被识别的新颖的LRR。新的LRR结构域存在于300多个蛋白质中，包括来自单细胞真核生物和细菌的真菌ECM33蛋白。

Leucine rich repeats (LRRs) are present in over 20,000 proteins from viruses to eukaryotes. Two to sixty-two LRRs occur in tandem. Most LRR proteins are involved in protein, ligand and in protein, protein interactions; these include the plant immune response and the mammalian innate immune response. Each repeat with 20-30 residues can be divided into a highly conserved segment and a variable segment. Eight classes have been recognized.Plant specific LRRs (class: PS-LRR) had previously been recognized in only plant proteins. However, we find that PS-LRRs are also present in twenty proteins from eleven bacterial species. We indicate that horizontal gene transfer of genes/gene fragments encoding PS-LRR domains occurred between bacteria and plants, as opposed to descent from a common ancestor. Also we find novel LRRs that were unrecognized until now. The novel LRR domains are present over three hundred proteins including fungal ECM33 protein from unicellular eukaryotes and bacteria.