De Samblanx G W, Fernandez del Carmen A, Sijtsma L, Plasman H H, Schaaper W M, Posthuma G A, Fant F, Meloen R H, Broekaert W F, van Amerongen A
Katholieke Universiteit Leuven, Heverlee, Belgium.
Pept Res. 1996 Nov-Dec;9(6):262-8.
Plant defensins are a class of cysteine-rich peptides of which several members have been shown to be potent inhibitors of fungal growth. A series of overlapping 15-mer peptides based on the amino acid sequence of the radish antifungal protein Rs-AFP2 have been synthesized. Peptides 6, 7, 8 and 9, comprising the region from cysteine 27 to cysteine 47 of Rs-AFP2 showed substantial antifungal activity against several fungal species (minimal inhibitory concentrations of 30-60 micrograms/mL), but no activity towards bacteria (except peptide 6 at 100 micrograms/mL). The active peptides were shown to be sensitive to the presence of cations in the medium and to the composition and pH of the medium. When present at a subinhibitory concentration (20 micrograms/mL), peptides 1, 7, 8 and 10 potentiated the activity of Rs-AFP2 from 2.3-fold to 2.8-fold. By mapping the characteristics of the active peptide on the structure of Rs-AFP2 as determined by nuclear magnetic resonance, the active region of the antifungal protein appears to involve beta-strands 2 and 3 in combination with the loop connecting those strands. A cyclized synthetic mimic of the loop, cysteine 36 to cysteine 45, was shown to have antifungal activity. Substitution of tyrosine 38 by alanine in the cyclic peptide substantially reduced the antifungal activity, indicating the importance of this residue for the activity of Rs-AFP2 as demonstrated carrier by mutational analysis.
植物防御素是一类富含半胱氨酸的肽，其中几个成员已被证明是真菌生长的有效抑制剂。基于萝卜抗真菌蛋白Rs-AFP2的氨基酸序列合成了一系列重叠的15聚体肽。包含Rs-AFP2从半胱氨酸27到半胱氨酸47区域的肽6、7、8和9对几种真菌具有显著的抗真菌活性（最低抑菌浓度为30 - 60微克/毫升），但对细菌无活性（肽6在100微克/毫升时除外）。活性肽对培养基中阳离子的存在以及培养基的组成和pH敏感。当以亚抑制浓度（20微克/毫升）存在时，肽1、7、8和10使Rs-AFP2的活性增强了2.3倍至2.8倍。通过将活性肽的特征映射到由核磁共振确定的Rs-AFP2结构上，抗真菌蛋白的活性区域似乎涉及β链2和3以及连接这些链的环。环（半胱氨酸36至半胱氨酸45）的环化合成模拟物显示具有抗真菌活性。在环肽中用丙氨酸取代酪氨酸38大大降低了抗真菌活性，如通过突变分析所证明的，表明该残基对Rs-AFP2活性的重要性。
