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Crystal structure of the Drosophila pattern-recognition receptor PGRP-SA
Structural highlights
FunctionPGPSA_DROME Peptidoglycan-recognition protein that plays a key role in innate immnunity by binding to peptidoglycans (PGN) of Gram-positive bacteria and activating the Toll pathway. Has no activity against on Gram-negative bacteria and fungi. Shows some partial redundancy with PRPGP-SD in Gram-positive bacteria recognition. May act by forming a complex with GNBP1 that activates the proteolytic cleavage of Spatzle and the subsequent activation of Toll pathway. Binds to diaminopimelic acid-type tetrapeptide PGN (DAP-type PGN) and lysine-type PGN (Lys-type PGN). Has some L,D-carboxypeptidase activity for DAP-type PGN, which are specific to prokaryotes, but not for Lys-type PGN.[1] [2] [3] [4] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedThe Drosophila peptidoglycan recognition protein SA (PGRP-SA) is critically involved in sensing bacterial infection and activating the Toll signaling pathway, which induces the expression of specific antimicrobial peptide genes. We have determined the crystal structure of PGRP-SA to 2.2-A resolution and analyzed its peptidoglycan (PG) recognition and signaling activities. We found an extended surface groove in the structure of PGRP-SA, lined with residues that are highly diverse among different PGRPs. Mutational analysis identified it as a PG docking groove required for Toll signaling and showed that residue Ser158 is essential for both PG binding and Toll activation. Contrary to the general belief that PGRP-SA has lost enzyme function and serves primarily for PG sensing, we found that it possesses an intrinsic L,D-carboxypeptidase activity for diaminopimelic acid-type tetrapeptide PG fragments but not lysine-type PG fragments, and that Ser158 and His42 may participate in the hydrolytic activity. As L,D-configured peptide bonds exist only in prokaryotes, this work reveals a rare enzymatic activity in a eukaryotic protein known for sensing bacteria and provides a possible explanation of how PGRP-SA mediates Toll activation specifically in response to lysine-type PG. A Drosophila pattern recognition receptor contains a peptidoglycan docking groove and unusual L,D-carboxypeptidase activity.,Chang CI, Pili-Floury S, Herve M, Parquet C, Chelliah Y, Lemaitre B, Mengin-Lecreulx D, Deisenhofer J PLoS Biol. 2004 Sep;2(9):E277. Epub 2004 Sep 7. PMID:15361936[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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