Department of Biochemistry & Nutrition, CSIR - Central Food Technological Research Institute, Mysore 570020, Karnataka, India.
Mol Immunol. 2014 Feb;57(2):119-28. doi: 10.1016/j.molimm.2013.08.010. Epub 2013 Oct 1.
Thaumatin-like proteins (TLPs) belong to the pathogenesis-related family (PR-5) of plant defense proteins. TLPs from only 32 plant genera have been identified as pollen or food allergens. IgE epitopes on allergens play a central role in food allergy by initiating cross-linking of specific IgE on basophils/mast cells. A comparative analysis of pollen- and food-allergenic TLPs is lacking. The main objective of this investigation was to study the structural and allergenicity features of sapodilla (Manilkara zapota) acidic TLP (TLP 1) by in silico methods. The allergenicity prediction of composite sequence of sapodilla TLP 1 (NCBI B3EWX8.1, G5DC91.1) was performed using FARRP, Allermatch and Evaller web tools. A homology model of the protein was generated using banana TLP template (1Z3Q) by HHPRED-MODELLER. B-cell linear epitope prediction was performed using BCpreds and BepiPred. Sapodilla TLP 1 matched significantly with allergenic TLPs from olive, kiwi, bell pepper and banana. IgE epitope prediction as performed using AlgPred indicated the presence of 2 epitopes (epitope 1: residues 36-48; epitope 2: residues 51-63), and a comprehensive analysis of all allergenic TLPs displayed up to 3 additional epitopes on other TLPs. It can be inferred from these analyses that plant allergenic TLPs generally carry 2-3 IgE epitopes. ClustalX alignments of allergenic TLPs indicate that IgE epitopes 1 and 2 are common in food allergenic TLPs, and IgE epitopes 2 and 3 are common in pollen allergenic TLPs; IgE epitope 2 overlaps with a portion of the thaumatin family signature. The secondary structural elements of TLPs vary markedly in regions 1 and 2 which harbor all the predicted IgE epitopes in all food and pollen TLPs in either of the region. Further, based on the number of IgE epitopes, food TLPs are grouped into rosid and non-rosid clades. The number and distribution of the predicted IgE epitopes among the allergenic TLPs may explain the specificity of food or pollen allergy as well as the varied degree of cross-reactivity among plant foods and/or pollens.
Thaumatin-like 蛋白（TLPs）属于植物防御蛋白的病程相关家族（PR-5）。只有 32 个植物属的 TLPs 被鉴定为花粉或食物过敏原。过敏原上的 IgE 表位通过交联嗜碱性粒细胞/肥大细胞上的特异性 IgE 在食物过敏中起核心作用。花粉和食物过敏原 TLPs 的比较分析尚缺乏。本研究的主要目的是通过计算机方法研究萨帕蒂拉（Manilkara zapota）酸性 TLP（TLP1）的结构和变应原性特征。使用 FARRP、Allermatch 和 Evaller 网络工具对萨帕蒂拉 TLP1（NCBI B3EWX8.1，G5DC91.1）的复合序列进行了变应原性预测。使用香蕉 TLP 模板（1Z3Q）通过 HHPRED-MODELLER 生成蛋白质的同源模型。使用 BCpreds 和 BepiPred 进行 B 细胞线性表位预测。萨帕蒂拉 TLP1 与橄榄、猕猴桃、甜椒和香蕉的过敏原 TLPs 显著匹配。使用 AlgPred 进行 IgE 表位预测表明存在 2 个表位（表位 1：残基 36-48；表位 2：残基 51-63），对所有过敏原 TLPs 的综合分析显示，其他 TLPs 上还有 3 个额外的表位。从这些分析中可以推断，植物过敏原 TLPs 通常携带 2-3 个 IgE 表位。过敏原 TLPs 的 ClustalX 比对表明，IgE 表位 1 和 2 在食物过敏原 TLPs 中常见，IgE 表位 2 和 3 在花粉过敏原 TLPs 中常见；IgE 表位 2 与 thaumatin 家族特征的一部分重叠。TLPs 的二级结构元件在区域 1 和 2 中差异显著，在该区域的所有食物和花粉 TLPs 中均存在所有预测的 IgE 表位。此外，基于 IgE 表位的数量，食物 TLPs 被分为蔷薇科和非蔷薇科分支。过敏原 TLPs 中预测的 IgE 表位的数量和分布可能解释了食物或花粉过敏的特异性，以及植物食物和/或花粉之间的交叉反应程度的差异。
