α-淀粉酶抑制剂AAI的核磁共振氢谱谱峰归属及结构分析

SEQUENCE-SPECIFIC 1H-NMR ASSIGNMENT OF PROTON RESONANCESOF THE AMARANTH α-AMYLASE INHIBITOR AAI AND STRUCTURE ANALYSIS

α -淀粉酶抑制剂AAI(α -AmylaseInhibitor)是从墨西哥苋属植物Amaranthushypochondriacus种子中提取的由32个氨基酸残基组成的多肽。它能强烈地抑制几种昆虫幼虫的α -淀粉酶活性 ,而不抑制人及哺乳类动物的α -淀粉酶活性。使用核磁共振方法收集了AAI的二维氢谱谱图 ,完成了全部主链和绝大部分侧链质子共振峰的序列归属 ,并利用X -PLOR软件计算出AAI的三维结构。AAI由三股反平行 β-折叠片与三对二硫键组成抑制剂胱氨酸结模体(inhibitorcystine -knotmotif)结构,与来自虎纹捕鸟蛛的神经毒素HWTX -I和凝集素SHL -I及其它来源的多种小分子活性多肽的结构类似 ,但它们的生物活力各不相同 ,表明该模体适用于结构功能关系的比较研究和作为蛋白质工程活力改造的结构骨架 (scaffold)。AAI对昆虫α -淀粉酶具有专一活性 ,可用于通过转基因技术来赋予植物抗虫活性。

The amaranth α-amylase inhibitor(AAI) is a 32 residue protein purified from seeds of the Mexican crop plant Amaranthus hypochondriacus. It specifically inhibits the activity of α-amylase in larvae of some insects but not human or other mammalian α-amylase. A set of 1H-2D NMR spectra were collected and the complete sequence-specific assignment of proton resonance in the spectra was described. The 3D structure of AAI was calculated by X-PLOR. It consists of a three stranded antiparallel β-sheet and three disulfide bridges, forming an inhibitor cystine-knot motif, shared by a small group of small peptides with diverse functions, including the neurotoxin HWTX-I and lectin SHL-I from the spider Selenocosmia huwena. This interesting feature makes the motif an ideal candidate for comparative structure-function relationship studies. It also implies the potentials of using this motif as a scaffold for the engineering of small peptides with altered biological activities. The insect specific α-amylase inhibitor activity of AAI can be transferred to crop plant by gene manipulation to protect them from predatory insects.