部分小麦低分子量谷蛋白亚基二级结构的预测与分析

为了从蛋白质高级结构的水平上研究小麦低分子量谷蛋白结构与功能的关系,利用互联网上开放的预测软件和蛋白质序列分析软件对已获得全序列,并明确其染色体定位的19个LMW-GS基因的推导氨基酸序列进行二级结构的预测和分析。结果表明,在整个LMW-GS二级结构中,无规则卷曲最多,达69.51%,α-螺旋(28.97%)较β-折叠(1.36%)占有绝对优势,因而归属于α结构型蛋白。其中,信号肽由大量α-螺旋和微量无规则卷曲组成,N-端和重复区均由无规则卷曲占据,而C-末端除富含α-螺旋和无规则卷曲外,还是β-折叠的唯一分布区。同时,两个分子间二硫键存在于无规则卷曲中,而另有6个分子内二硫键分布于α-螺旋内或其附近,由此推导出小麦LMW-GS二级结构的平面模式图。这种特异的LMW-GS二级结构不仅进一步证明了“蛋白质一级结构决定高级结构”,以及信号肽引导新合成的LMW-GS顺利进入相应细胞器等经典理论,而且从空间结构的水平上阐释了LMW-GS多肽链致密化及其互聚体形成、富集,并与HMW-GS一起影响面粉加工品质的结构基础。

Prediction and Analysis of Secondary Structure of Low Molecular Weight Glutenin Subunits in Wheat

In order to study relationship between the secondary structure and functions of low-molecular-weight glutenin subunits, the secondary structures of the putative amino acid sequences from 19 LMW-GS gene known whole coding region and chromosomal location were predicted by softwares of predicting protein in internet. The results show that, in the secondary structure of LMW-GS, coil content is the highest, to 69.51%. In comparison with β-sheet at 1.33%, α-helix at 28.97% is outstandingly high, implying that LMW-GS belongs to α-class protein according to the protein structural class. The signal peptide consists of abundant α-helix and little coil. Both the N-terminal region and the repetitive region are occupied by coil. The C-terminal region is rich in α-helix and coil, besides little β-sheet. Meanwhile two intermolecular disulfide bonds are situated in coil, while the other six intra-molecular disulfide bonds are situated in or close to the α-helix. Diagram representing the secondary structures of typical LMW-GS is drawn based on types in combination with both their frequencies and distributions of the predicted protein secondary structures. The result might not only prove classic theories, like primary structure determining the higher structures of protein and the basic function of synthesized proteins into proper cytoplasm, but also explain the structural basis of the hardness, enrichment and polymerized of multi-peptides chains with HMW-GS influencing the technological properties of wheat flour.