Biotoxin Units of Key Laboratory of Animal Models and Human Disease Mechanisms, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, 650223 Yunnan, China.
Amino Acids. 2012 Aug;43(2):677-85. doi: 10.1007/s00726-011-1116-7. Epub 2011 Oct 19.
Cathelicidins comprise a family of antimicrobial peptides (AMPs) sharing a highly conserved cathelin domain, and play a central role in the innate defense against infection in most of vertebrates. But so far it has not yet been found in amphibians although a large number of other groups of AMPs have been identified. In the current work, the first amphibian cathelicidin (cathelicidin-AL) has been characterized from the frog skin of Amolops loloensis. Cathelicidin-AL (RRSRRGRGGGRRGGSGGRGGRGGGGRSGAGSSIAGVGSRGGGGGRHYA) is a cationic peptide containing 48 amino acid residues (aa) with 12 basic aa and no acidic aa. The chemical synthesized peptide efficiently killed bacteria and some fungal species including clinically isolated drug-resistance microorganisms. The cDNA encoding cathelicidin-AL precursor was cloned from the skin cDNA library of A. loloensis. As other cathelicidins, the precursor of cathelicidin-AL also contains highly conserved anionic cathelin domain of cysteine proteinase inhibitor followed by the AMP fragment at C-terminus. Phylogenetic analysis revealed that as connecting link, the amphibian cathelicidin predates reptilia but postdates fish cathelicidin. The peptide purification combined with gene cloning results confirms the presence of cathelicidin in amphibians and filled the evolutionary gap of cathelicidin in vertebrate, considering amphibians' special niche as the animals bridging the evolutionary land-water gap.
抗菌肽（AMPs）包含一个家族，它们具有高度保守的抗菌肽前体结构域，在脊椎动物的先天抗感染防御中起着核心作用。但到目前为止，在两栖动物中还没有发现抗菌肽，尽管已经鉴定出大量其他 AMPs 家族。在目前的工作中，从四川山鹧鸪（Amolops loloensis）的皮肤中鉴定出了第一个两栖动物抗菌肽（cathelicidin-AL）。抗菌肽-AL（RRSRRGRGGGRRGGSGGRGGRGGGGRSGAGSSIAGVGSRGGGGGRHYA）是一种阳离子肽，含有 48 个氨基酸残基（aa），其中 12 个为碱性 aa，没有酸性 aa。化学合成的肽能够有效杀死细菌和一些真菌，包括临床分离的耐药微生物。从四川山鹧鸪皮肤 cDNA 文库中克隆了编码抗菌肽-AL 前体的 cDNA。与其他抗菌肽一样，抗菌肽-AL 的前体也含有高度保守的含半胱氨酸蛋白酶抑制剂的阴离子抗菌肽前体结构域，其后是 C 末端的 AMP 片段。系统进化分析表明，作为连接环节，两栖动物抗菌肽的出现先于爬行动物，但晚于鱼类抗菌肽。肽的纯化结合基因克隆结果证实了两栖动物抗菌肽的存在，填补了脊椎动物抗菌肽进化的空白，考虑到两栖动物作为连接进化陆地和水域鸿沟的动物的特殊生态位。
