Peptidoglycan recognition protein

Peptidoglycan recognition proteins (PGRPs) 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.[1][2] In mammals, PGRPs kill bacteria directly by interacting with their peptidoglycan cell wall.[2]

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.[3]

Types

Insects generate up to 19 alternatively spliced PGRPs, classified into long (L) and short (S) forms. For instance, the fruit fly (Drosophila melanogaster) expresses 13 PGRPs which are alternatively spliced into 19 proteins, while the mosquito (Anopheles gambiae) expresses 7 PGRPs, with 9 splice variants.[1]

Mammals have up to four PGRPs, all of which are secreted. These are peptidoglycan recognition protein 1 (PGLYRP1), peptidoglycan recognition protein 2 (PGLYRP2), peptidoglycan recognition protein 3 (PGLYRP3) and peptidoglycan recognition protein 4 (PGLYRP4).[2]

References
  1. Royet, Julien; Gupta, Dipika; Dziarski, Roman (11 November 2011). "Peptidoglycan recognition proteins: modulators of the microbiome and inflammation". Nature Reviews Immunology. 11: 837–51. doi:10.1038/nri3089. PMID 22076558.
  2. Dziarski, R (February 2004). "Peptidoglycan recognition proteins (PGRPs)". Molecular Immunology. 40 (12): 877–886. doi:10.1016/j.molimm.2003.10.011. PMC 1779587.
  3. Dziarski, Roman; Gupta, Dipika (2006). "The peptidoglycan recognition proteins (PGRPs)". Genome Biology. 7 (8): 232. doi:10.1186/gb-2006-7-8-232. PMC 1779587.
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