Recombinant Mouse PGLYRP1/PGRP-S Protein

The mouse PGRP family comprises four peptidoglycan recognition proteins that may function as innate immunity pattern recognition molecules (1, 2). Termed PGRP-L, PGRP-I alpha, PGRP-I beta and PGRP-S, they are all products of separate genes, and all are named for the relative length of their translated product (3). PGRP-L (for long) is 530 amino acids (aa) in length, while PGRP-I alpha and I beta are intermediate (I) in length at 347 aa and 374 aa, respectively, and PGRP-S is shortest at 182 aa in length (3, 4). All mouse PGRPs bind peptidoglycan and Gram-positive bacteria, and all have at least three C-terminal PGRP domains at variable sites that are highly conserved from insects to mammals (3). Mouse PGRP-S, the first described member of the family, is an 18 kDa secreted protein associated with neutrophils (4, 5). The mature molecule is 166 aa in length and presumably contains three variably-sized peptide-carbohydrate recognition sequences. Mouse PGRP-S is 86%, 69% and 72% aa identical to rat, bovine and human mature PGRP‑S, respectively. Studies with PGRP-S deficient mice indicate that knock-out mice have increased susceptibility to infections with low (but not high) pathogenicity bacteria. Neutrophils from knock-out mice exhibit normal phagocytosis of bacteria but are defective in intracellular killing and digestion of nonpathogenic bacteria (5). The three longer PGRP members are all membrane-bound molecules that contain two membrane-spanning segments. Both the N- and C‑termini are depicted as being extracellular with a joining cytoplasmic domain. All three transmembrane forms show at least one PGRP domain on the C‑terminal extracellular region; other PGRP domains are variably distributed over their two extracellular and one cytoplasmic region (3).