Department of Biotechnology, Indian Institute of Technology Roorkee, Roorkee 247 667, India.
J Mol Evol. 2011 Dec;73(5-6):369-79. doi: 10.1007/s00239-012-9484-5. Epub 2012 Jan 25.
Miraculin-like proteins (MLPs) belong to soybean Kunitz super-family and have been characterized from many plant families like Rutaceae, Solanaceae, Rubiaceae, etc. Many of them possess trypsin inhibitory activity and are involved in plant defense. MLPs exhibit significant sequence identity (30-95%) to native miraculin protein, also belonging to Kunitz super-family compared with a typical Kunitz family member (30%). The sequence and structure-function comparison of MLPs with that of a classical Kunitz inhibitor have demonstrated that MLPs have evolved to form a distinct group within Kunitz super-family. Sequence analysis of new genes along with available MLP sequences in the literature revealed three major groups for these proteins. A significant feature of Rutaceae MLP type 2 sequences is the presence of phosphorylation motif. Subtle changes are seen in putative reactive loop residues among different MLPs suggesting altered specificities to specific proteases. In phylogenetic analysis, Rutaceae MLP type 1 and type 2 proteins clustered together on separate branches, whereas native miraculin along with other MLPs formed distinct clusters. Site-specific positive Darwinian selection was observed at many sites in both the groups of Rutaceae MLP sequences with most of the residues undergoing positive selection located in loop regions. The results demonstrate the sequence and thereby the structure-function divergence of MLPs as a distinct group within soybean Kunitz super-family due to biotic and abiotic stresses of local environment.
Miraculin-like 蛋白 (MLPs) 属于大豆 Kunitz 超家族，已从芸香科、茄科、茜草科等许多植物科中得到鉴定。它们中的许多具有胰蛋白酶抑制活性，并参与植物防御。MLPs 与天然 miraculin 蛋白具有显著的序列同一性（30-95%），也属于 Kunitz 超家族，而与典型的 Kunitz 家族成员 (30%)相比。MLPs 的序列和结构-功能与经典 Kunitz 抑制剂的比较表明，MLPs 在 Kunitz 超家族内已经进化形成了一个独特的群体。对新基因的序列分析以及文献中可用的 MLP 序列表明，这些蛋白质可以分为三大类。芸香科 MLP 类型 2 序列的一个显著特征是存在磷酸化模体。不同 MLP 中假定的反应环残基的细微变化表明对特定蛋白酶的特异性发生了改变。在系统发育分析中，芸香科 MLP 类型 1 和类型 2 蛋白聚集在不同的分支上，而天然 miraculin 与其他 MLP 形成了不同的簇。在两个芸香科 MLP 序列组中，许多位点都观察到了特异性正达尔文选择，大多数经历正选择的残基位于环区。结果表明，由于当地环境的生物和非生物胁迫，MLPs 作为大豆 Kunitz 超家族中的一个独特群体，其序列和结构-功能已经发生了分化。
