Department of Ecological and Biological Sciences, University of Tuscia, Via S. Camillo de Lellis, Viterbo, Italy
Biol Chem. 2012 Aug 4;0(0):1-14. doi: 10.1515/hsz-2012-0225.
Plants possess an innate immune system enabling them to defend themselves against pathogen attack. The accumulation of newly synthesized pathogenesis-related proteins (PRs) is one of the most studied inducible plant defence response. In this paper, we report on the characterization of a class I PR4 vacuolar protein from Arabidopsis, named AtHEL. The protein has a modular structure consisting of an N-terminal hevein-like domain (CB-HEL) and a C-terminal domain (CD-HEL) that are posttranslationally processed. Both domains show a strong antifungal activity, but they do not have chitinolitic properties. CD-HEL was found to be endowed with RNase, but not DNase activity. Molecular modeling carried out on both domains revealed that CB-HEL possesses a chitin binding site strictly conserved between hevein-type peptides and that the cavity involved in substrate interaction of CD-HEL do not show any residue substitution with respect to the orthologous wheatwin1 from wheat. Using a fishing for partners approach, CB-HEL was found to interact with a fungal fruiting body lectin. According to literature, we can hypothesize that CB-HEL could cross the pathogen hyphal membrane and that its interaction with a fungal lectin could knock out one of the weapons that the fungus uses.
植物具有先天免疫系统，使它们能够抵御病原体的攻击。研究最多的植物诱导防御反应之一是新合成的与发病相关的蛋白质 (PR) 的积累。在本文中，我们报告了拟南芥一类 PR4 液泡蛋白 AtHEL 的特性。该蛋白具有模块化结构，由 N 端的海豆荚素样结构域 (CB-HEL) 和 C 端结构域 (CD-HEL) 组成，这两个结构域在后翻译过程中被加工。这两个结构域都具有很强的抗真菌活性，但没有几丁质酶活性。发现 CD-HEL 具有 RNase 活性，但没有 DNase 活性。对这两个结构域进行的分子建模表明，CB-HEL 具有严格保守的几丁质结合位点，与海豆荚素肽之间的几丁质结合位点相同，并且 CD-HEL 参与底物相互作用的腔与同源小麦中的 wheatwin1 没有任何残基取代。使用钓取伴侣的方法，发现 CB-HEL 与真菌子实体凝集素相互作用。根据文献，我们可以假设 CB-HEL 可以穿过病原体菌丝膜，其与真菌凝集素的相互作用可以消除真菌使用的武器之一。
