Peptidoglycan recognition protein
Peptidoglycan recognition proteins are a group of highly conserved pattern recognition receptors with at least one peptidoglycan recognition domain capable of recognizing the peptidoglycan wall of bacteria. They are present in insects, mollusks, echinoderms and chordates. The mechanism of action of PGRPs varies between taxa. In insects, PGRPs kill bacteria indirectly by activating one of four unique effector pathways: prophenoloxidase cascade, activation of Toll pathway, activation of IMD pathway, and induction of phagocytosis. In mammals, PGRPs kill bacteria directly by interacting with their peptidoglycan cell wall.Structure
PGRPs contain at least one C-terminal peptidoglycan recognition domain, which is about 165 amino acids long. This peptidoglycan-binding type 2 amidase domain is homologous to bacteriophage and bacterial type 2 amidases.Types
Insects generate up to 19 alternatively spliced PGRPs, classified into long and short forms. For instance, the fruit fly expresses 13 PGRPs which are alternatively spliced into 19 proteins, while the mosquito expresses 7 PGRPs, with 9 splice variants.
Mammals have up to four PGRPs, all of which are secreted. These are peptidoglycan recognition protein 1, peptidoglycan recognition protein 2, peptidoglycan recognition protein 3 and peptidoglycan recognition protein 4.
