The role of a novel secretory peptidoglycan recognition protein with antibacterial ability from the Chinese Oak Silkworm Antheraea pernyi in humoral immunity

Peptidoglycan recognition proteins (PGRPs) are a family of pattern recognition receptors that play a critical role in the immune response of invertebrates and vertebrates. Herein, the short Ap PGRP-D gene was cloned from the model lepidopteran Antheraea pernyi. Quantitative PCR (qPCR) confirmed that Ap PGRP-D is an immune-related protein and that the expression of Ap PGRP-D can be induced by microorganisms. Ap PGRP-D is a broad-spectrum pattern recognition protein that activates the prophenoloxidase cascade activation system and promotes the agglutination of microbial cells. Likely due to its amidase activity, Ap PGRP-D can inhibit the growth of E. coli and S. aureus . In addition, we demonstrated for the first time that zinc ions, as important metal coenzymes, could promote multiple functions of Ap PGRP-D but not its amidase activity.