Department of Marine Life Sciences, School of Marine Biomedical Sciences, Jeju National University, Jeju Self-Governing Province 690-756, Republic of Korea.
Fish Shellfish Immunol. 2013 Nov;35(5):1369-79. doi: 10.1016/j.fsi.2013.07.048. Epub 2013 Aug 20.
Lysozymes are ubiquitously distributed enzymes with hydrolytic activity against bacterial peptidoglycan and function to protect organisms from microbial pathogens. In this study, an invertebrate goose-type lysozyme, designated as abLysG, was identified in the disk abalone, Haliotis discus discus. The full-length cDNA of abLysG was 894 bp in length with an open reading frame of 789 bp encoding a polypeptide of 263 amino acids containing a signal peptide and a characteristic soluble lytic transglycosylase domain. Six cysteine residues and two catalytic residues (Glu(142) and Asp(168)) conserved among molluscs were also identified. The 3D homology structural models of abLysG and hen egg white lysozyme had similar conformations of the active sites involved in the binding of substrate. BAC sequence data revealed that the genomic structure of disk abalone g-type lysozyme comprises 7 exons with 6 intervening introns. The deduced amino acid sequence of abLysG shared 45.2-61.6% similarity with those of other molluscs and vertebrates. The TFSEARCH server predicted a variety of transcription factor-binding sites in the 5'-flanking region of the abLysG gene, some of which are involved in transcriptional regulation of the lysozyme gene. abLysG expression was detected in multiple tissues with the highest expression in mantle. Moreover, qPCR analysis of abLysG mRNA expression demonstrated significant up-regulation in gill in response to infection by live bacteria (Vibrio parahaemolyticus and Listeria monocytogenes), virus (viral hemorrhagic septicemia) and bacterial mimics (LPS and PGN). Expression of the recombinant disk abalone g-type lysozyme in Escherichia coli BL21, demonstrated its bacteriolytic activity against several Gram-negative and Gram-positive bacterial species. Collectively these data suggest that abLysG is an antimicrobial enzyme with a potential role in the disk abalone innate immune system to protect it from bacterial and viral infections.
溶菌酶是一种广泛分布的酶，具有水解细菌肽聚糖的活性，可保护生物免受微生物病原体的侵害。在本研究中，从盘鲍（Haliotis discus discus）中鉴定出一种无脊椎动物鹅型溶菌酶，命名为 abLysG。abLysG 的全长 cDNA 长 894bp，开放阅读框为 789bp，编码 263 个氨基酸的多肽，含有信号肽和特征性可溶性溶菌转糖苷酶结构域。还鉴定了 6 个半胱氨酸残基和 2 个催化残基（Glu（142）和 Asp（168）），这些残基在软体动物中是保守的。abLysG 和鸡卵清溶菌酶的 3D 同源结构模型具有相似的活性部位构象，参与了底物的结合。BAC 序列数据显示，盘鲍 g 型溶菌酶的基因组结构由 7 个外显子和 6 个内含子组成。abLysG 的推导氨基酸序列与其他软体动物和脊椎动物的相似性为 45.2-61.6%。TFSEARCH 服务器预测了 abLysG 基因 5'-侧翼区的多种转录因子结合位点，其中一些位点参与了溶菌酶基因的转录调控。abLysG 在多种组织中均有表达，其中在套膜中表达量最高。此外，qPCR 分析显示，abLysGmRNA 在鳃中对活细菌（副溶血弧菌和单核细胞增生李斯特菌）、病毒（病毒性出血性败血症）和细菌模拟物（LPS 和 PGN）的感染有显著上调。在大肠杆菌 BL21 中表达重组盘鲍 g 型溶菌酶，显示其对几种革兰氏阴性和革兰氏阳性细菌具有溶菌活性。这些数据表明，abLysG 是一种抗菌酶，在盘鲍固有免疫系统中具有潜在的作用，可保护其免受细菌和病毒感染。
