Peptidoglycan recognition proteins (PGRPs), which are structurally conserved innate immune molecules in invertebrate and vertebrate animals, play the important roles in regulation of innate immune responses. In this paper, three PGRP genes of spotted sea bass, Lateolabrax maculatus, were cloned, designated as Ssb-PGRP2, Ssb-PGRP-L2 and Ssb-PGRP-SC2, respectively. Sequence analysis showed that the deduced amino acid sequences of Ssb-PGRP2, Ssb-PGRP-L2 and Ssb-PGRP-SC2 proteins contained respectively 468, 482 and 167 amino acid residues, and had the typical structural features of PGRPs, i.e. conserved PGRP domain and Zn²⁺ binding domain including four specific amino acid residues which were required for amidase activity. q-PCR analysis of total mRNA showed that the mRNA expression of three PGRP genes were detected in all the examined tissues and the expression patterns of Ssb-PGRP2, Ssb-PGRP-L2 and Ssb-PGRP-SC2 were different. After injected with LPS, Poly (I:C) and Edwardsiella tarda, there was a clear time-dependent expression pattern for each of the three PGRP genes in head kidney, spleen, intestine and gill of the spotted sea bass. In our study, three recombinant proteins corresponding to the three members of the peptidoglycan recognition protein family were expressed and purified. Moreover, all of the three recombinant PGRP proteins significantly inhibited bacterial survival and growth, and expressed bactericidal effects on Vibrio harveyi, Staphylococcus aureus and Edwardsiella tarda. In particular, it was firstly verified that their antimicrobial activity presented the superimposed effect. Overall, these findings indicated that three PGRP genes of spotted sea bass were at least involved in host defense against bacterial infections.

肽聚糖识别蛋白（PGRP）在无脊椎动物和脊椎动物中是结构保守的先天免疫分子，在调节先天免疫应答中起重要作用。本文克隆了斑点鲈鱼的三个PGRP基因，即Laterolabrax maculatus，分别命名为Ssb-PGRP2，Ssb - PGRP-L2和Ssb-PGRP-SC2。序列分析表明，Ssb-PGRP2，Ssb-PGRP-L2和Ssb-PGRP-SC2蛋白的推导氨基酸序列分别含有468、482和167个氨基酸残基，具有PGRP的典型结构特征，即保守的PGRP结构域和锌²⁺结合结构域，包括酰胺酶活性所需的四个特定氨基酸残基。总mRNA的q-PCR分析显示，在所有检查的组织中均检测到三个PGRP基因的mRNA表达，并且Ssb-PGRP2，Ssb-PGRP-L2和Ssb-PGRP-SC2的表达模式不同。注射LPS，Poly（I：C）和爱德华氏菌，斑点海鲈的头肾，脾，肠和and中的三个PGRP基因中的每一个都有明显的时间依赖性表达模式。在我们的研究中，表达并纯化了与肽聚糖识别蛋白家族的三个成员相对应的三个重组蛋白。而且，所有三种重组PGRP蛋白均显着抑制细菌存活和生长，并对哈维弧菌，金黄色葡萄球菌和塔氏爱德华氏菌表达杀菌作用。特别是，首先证实其抗菌活性具有叠加作用。总体而言，这些发现表明，三种PGRP 斑点鲈鱼的基因至少参与了宿主抵抗细菌感染的防御。