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1s2j
From Proteopedia
Crystal structure of the Drosophila pattern-recognition receptor PGRP-SA
Overview
The 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.
About this Structure
1S2J is a Single protein structure of sequence from Drosophila melanogaster. Full crystallographic information is available from OCA.
Reference
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 Page seeded by OCA on Sat May 3 08:13:02 2008
