Wong Ka H, Tan Wei Liang, Kini Shruthi G, Xiao Tianshu, Serra Aida, Sze Sui Kwan, Tam James P
School of Biological Sciences, Nanyang Technological UniversitySingapore, Singapore.
Front Plant Sci. 2017 Jun 21;8:1100. doi: 10.3389/fpls.2017.01100. eCollection 2017.
Hevein and hevein-like peptides are disulfide-constrained chitin-binding cysteine-rich peptides. They are divided into three subfamilies, 6C-, 8C-, and 10C-hevein-like peptides, based on the number of cysteine residues. In addition, hevein-like peptides can exist in two forms, short and long. The long C-terminal form found in hevein and 10C-hevein-like peptides contain a C-terminal protein cargo. In contrast, the short form without a protein cargo is found in all three subfamilies. Here, we report the discovery and characterization of two novel glutamine-rich and protein cargo-free 8C-hevein-like peptides, vaccatides vH1 and vH2, from of the Caryophyllaceae family. Proteomic analyses showed that the vaccatides are 40-41 amino acids in length and contain a chitin-binding domain. NMR determination revealed that vaccatide vH2 displays a highly compact structure with a N-terminal cystine knot and an addition C-terminal disulfide bond. Stability studies showed that this compact structure renders vaccatide vH2 resistant to thermal, chemical and proteolytic degradation. The chitin-binding vH2 was shown to inhibit the mycelium growth of four phyto-pathogenic fungal strains with IC values in the micromolar range. Our findings show that vaccatides represent a new family of 8C-hevein-like peptides, which are protein cargo-free and glutamine-rich, characteristics that differentiate them from the prototypic hevein and the 10C-hevein-like peptides. In summary, this study enriches the existing library of hevein-like peptides and provides insight into their molecular diversity in sequence, structure and biosynthesis. Additionally, their highly disulfide-constrained structure could be used as a scaffold for developing metabolically and orally active peptidyl therapeutics.
橡胶素和类橡胶素肽是二硫键约束的富含半胱氨酸的几丁质结合肽。它们根据半胱氨酸残基的数量分为三个亚家族，即6C-、8C-和10C-类橡胶素肽。此外，类橡胶素肽可以以两种形式存在，即短形式和长形式。在橡胶素和10C-类橡胶素肽中发现的长C末端形式含有一个C末端蛋白负载。相比之下，在所有三个亚家族中都发现了没有蛋白负载的短形式。在此，我们报告了从石竹科植物中发现并鉴定出两种新型的富含谷氨酰胺且无蛋白负载的8C-类橡胶素肽，即vaccatides vH1和vH2。蛋白质组学分析表明，vaccatides长度为40 - 41个氨基酸，含有一个几丁质结合结构域。核磁共振测定显示，vaccatide vH2具有高度紧凑的结构，带有一个N末端胱氨酸结和一个额外的C末端二硫键。稳定性研究表明，这种紧凑结构使vaccatide vH2对热、化学和蛋白水解降解具有抗性。几丁质结合的vH2被证明能抑制四种植物病原真菌菌株的菌丝体生长，其IC值在微摩尔范围内。我们的研究结果表明，vaccatides代表了一个新的8C-类橡胶素肽家族，它们无蛋白负载且富含谷氨酰胺，这些特征将它们与原型橡胶素和10C-类橡胶素肽区分开来。总之，这项研究丰富了现有的类橡胶素肽文库，并为它们在序列、结构和生物合成方面的分子多样性提供了见解。此外，它们高度受二硫键约束的结构可作为开发代谢活性和口服活性肽类治疗药物的支架。
