A peptidoglycan recognition protein from Sciaenops ocellatus is a zinc amidase and a bactericide with a substrate range limited to Gram-positive bacteria

• Published in: Fish & Shellfish Immunology
• Main Authors: Li, Mo-Fei, Zhang, Min, Wang, Chun-Lin, Sun, Li, Sun, L (reprint author), Chinese Acad Sci, Inst Oceanol, Key Lab Expt Marine Biol, 7 Nanhai Rd, Qingdao 266071, Peoples R China.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2012
• Subjects: Peptidoglycan Recognition Protein; Amidase; Sciaenops Ocellatus; Bactericide; Fisheries; Immunology; Marine & Freshwater Biology; Veterinary Sciences; Red drum; Sciaenops ocellatus
• Online Access: http://ir.qdio.ac.cn/handle/337002/12266; https://doi.org/10.1016/j.fsi.2011.11.024

Peptidoglycan recognition proteins (PGRPs) are a family of innate immune molecules that recognize bacterial peptidoglycan. PGRPs are highly conserved in invertebrates and vertebrates including fish. However, the biological function of teleost PGRP remains largely uninvestigated. In this study, we identified a PGRP homologue, SoPGLYRP-2, from red drum (Sciaenops ocellatus) and analyzed its activity and potential function. The deduced amino acid sequence of SoPGLYRP-2 is composed of 482 residues and shares 46-94% overall identities with known fish PGRPs. SoPGLYRP-2 contains at the C-terminus a single zinc amidase domain with conserved residues that form the catalytic site. Quantitative RT-PCR analysis detected SoPGLYRP-2 expression in multiple tissues, with the highest expression occurring in liver and the lowest expression occurring in brain. Experimental bacterial infection upregulated SoPGLYRP-2 expression in kidney, spleen, and liver in time-dependent manners. To examine the biological activity of SoPGLYRP-2, purified recombinant proteins representing the intact SoPGLYRP-2 (rSoPGLYRP-2) and the amidase domain (rSoPGLYRP-AD) were prepared from Escherichia coli. Subsequent analysis showed that rSoPGLYRP-2 and rSoPGLYRP-AD (i) exhibited comparable Zn2+-dependent peptidoglycanlytic activity and were able to recognize and bind to live bacterial cells, (ii) possessed bactericidal effect against Gram-positive bacteria and slight bacteriostatic effect against Gram-negative bacteria, (iii) were able to block bacterial infection into host cells. These results indicate that SoPGLYRP-2 is a zinc-dependent amidase and a bactericide that targets preferentially at Gram-positive bacteria, and that SoPGLYRP-2 is likely to play a role in host innate immune defense during bacterial infection. (C) 2011 Elsevier Ltd. All rights reserved.