Xiao Xun, Zhang Yanqi, Liao Zhiwei, Su Jianguo
Department of Aquatic Animal Medicine, College of Fisheries, Huazhong Agricultural University, No. 1 Shizishan St., Wuhan 430070, China.
Laboratory for Marine Biology and Biotechnology, Pilot National Laboratory for Marine Science and Technology, Qingdao 266237, China.
Antibiotics (Basel). 2020 Feb 12;9(2):78. doi: 10.3390/antibiotics9020078.
Fish are a potential source of diverse organic compounds with a broad spectrum of biological activities. Many fish-derived antimicrobial peptides and proteins are key components of the fish innate immune system. They are also potential candidates for development of new antimicrobial agents. CXCL20b is a grass carp (Ctenopharyngodon idella) CXC chemokine strongly transcribed at the early stage of bacterial infections, for which the immune role had not been reported to date. In the present study, we found that CXCL20b is a cationic amphipathic protein that displays potent antimicrobial activity against both Gram-positive and Gram-negative bacteria. The results of DiOC(3) and atomic force microscopy (AFM) assays indicated that CXCL20b could induce bacterial membrane depolarization and disruption in a short time. By performing further structure-activity studies, we found that the antimicrobial activity of CXCL20b was mainly relative to the N-terminal random coil region. The central part of this cytokine representing β-sheet region was insoluble in water and the C-terminal α-helical region did not show an antimicrobial effect. The results presented in this article support the poorly understood function of CXCL20b, which fulfills an important role in bony fish antimicrobial immunity.
鱼类是多种具有广泛生物活性的有机化合物的潜在来源。许多鱼类衍生的抗菌肽和蛋白质是鱼类先天免疫系统的关键组成部分。它们也是开发新型抗菌剂的潜在候选物。CXCL20b是一种草鱼（Ctenopharyngodon idella）CXC趋化因子，在细菌感染早期强烈转录，其免疫作用迄今尚未见报道。在本研究中，我们发现CXCL20b是一种阳离子两亲性蛋白，对革兰氏阳性菌和革兰氏阴性菌均具有强大的抗菌活性。DiOC(3)和原子力显微镜（AFM）分析结果表明，CXCL20b可在短时间内诱导细菌膜去极化和破坏。通过进一步的构效关系研究，我们发现CXCL20b的抗菌活性主要与N端无规卷曲区域有关。该细胞因子代表β-折叠区域的中部不溶于水，C端α-螺旋区域未显示抗菌作用。本文给出的结果支持了对CXCL20b功能了解较少的情况，其在硬骨鱼抗菌免疫中发挥着重要作用。
