School of Marine Sciences, Ningbo University, Ningbo 315211, PR China.
School of Marine Sciences, Ningbo University, Ningbo 315211, PR China.
Fish Shellfish Immunol. 2018 Aug;79:321-326. doi: 10.1016/j.fsi.2018.05.037. Epub 2018 May 25.
Lysozyme is a key component of the innate immune system, which plays a pivotal role in early defense against pathogen infection. In this study, an i-type lysozyme homology was identified from the razor clam Sinonovacula constricta (designated as ScLYZ) through RACE approaches. The full-length cDNA of ScLYZ was 768 bp and encoded a polypeptide of 140 amino acid residues. SMART analysis revealed that ScLYZ processed a signal peptide (1-18 aa) and a destabilase domain from 25 to 133 aa. Two catalytic residues (Glu and Asp) and two specific motifs ["CL(E/L/R/H)C(I/M)C" and "MDVGSLSCG(P/Y) (F/Y)QIK"] of the i-type lysozyme were highly conserved in the ScLYZ sequence. Multiple sequence alignments and phylogenetic analysis indicated that ScLYZ could be a new member of the i-type lysozyme subfamily. Tissue distribution analysis revealed that ScLYZ was constitutively expressed in all examined tissues, and the highest expression was found in the hepatopancreas. After the razor clams were challenged by Vibrio parahaemolyticus, the mRNA levels of ScLYZ increased in the gill and hepatopancreas. Moreover, the recombinant protein was expressed in Escherichia coli, and the refolded ScLYZ showed highly antimicrobial activities against V. parahaemolyticus and Vibrio splendidus. The minimal inhibitory concentration toward V. parahaemolyticus was 8.2 μmol/mL. All our results supported that ScLYZ was involved in the innate immune defense of razor clam by inhibiting the growth of invasive pathogens.
溶菌酶是先天免疫系统的关键组成部分，在抵御病原体感染的早期防御中发挥着关键作用。本研究通过 RACE 方法从缢蛏（Sinonovacula constricta）中鉴定出一种 i 型溶菌酶同源物（命名为 ScLYZ）。ScLYZ 的全长 cDNA 为 768 bp，编码 140 个氨基酸残基的多肽。SMART 分析表明，ScLYZ 加工了一个信号肽（1-18 aa）和一个从 25 到 133 aa 的不稳定酶结构域。两个催化残基（Glu 和 Asp）和两个 i 型溶菌酶的特定基序 ["CL(E/L/R/H)C(I/M)C" 和 "MDVGSLSCG(P/Y) (F/Y)QIK"] 在 ScLYZ 序列中高度保守。多序列比对和系统发育分析表明，ScLYZ 可能是 i 型溶菌酶亚家族的一个新成员。组织分布分析表明，ScLYZ 在所有检测到的组织中均持续表达，在肝胰腺中表达量最高。在缢蛏受到副溶血弧菌攻击后，ScLYZ 的 mRNA 水平在鳃和肝胰腺中增加。此外，重组蛋白在大肠杆菌中表达，复性的 ScLYZ 对副溶血弧菌和灿烂弧菌表现出高度的抗菌活性。对副溶血弧菌的最小抑菌浓度为 8.2 μmol/mL。我们的所有结果都支持 ScLYZ 通过抑制入侵病原体的生长参与了缢蛏的先天免疫防御。
