title: Multiligand specificity of pathogen-associated molecular pattern-binding site in peptidoglycan recognition protein.
abstract: The peptidoglycan recognition protein PGRP-S is an innate immunity molecule that specifically interacts with microbial peptidoglycans and other pathogen-associated molecular patterns. We report here two structures of the unique tetrameric camel PGRP-S (CPGRP-S) complexed with (i) muramyl dipeptide (MDP) at 2.5 Å resolution and (ii) GlcNAc and β-maltose at 1.7Å resolution. The binding studies carried out using surface plasmon resonance indicated that CPGRP-S binds to MDP with a dissociation constant of 10(-7) M, whereas the binding affinities for GlcNAc and β-maltose separately are in the range of 10(-4) M to 10(-5) M, whereas the dissociation constant for the mixture of GlcNAc and maltose was estimated to be 10(-6) M. The data from bacterial suspension culture experiments showed a significant inhibition of the growth of Staphylococcus aureus cells when CPGRP-S was added to culture medium. The ELISA experiment showed that the amount of MDP-induced production of TNF-α and IL-6 decreased considerably after the introduction of CPGRP-S. The crystal structure determinations of (i) a binary complex with MDP and (ii) a ternary complex with GlcNAc and β-maltose revealed that MDP, GlcNAc, and β-maltose bound to CPGRP-S in the ligand binding cleft, which is situated at the interface of molecules C and D of the homotetramer formed by four protein molecules A, B, C, and D. In the binary complex, the muramyl moiety of MDP is observed at the C-D interface, whereas the peptide chain protrudes into the center of tetramer. In the ternary complex, GlcNAc and β-maltose occupy distinct non-overlapping positions belonging to different subsites.
authors.affiliation: Department of Biophysics, All India Institute of Medical Sciences, New Delhi, India 110029.
authors.forename: Pradeep
authors.initials: P
authors.lastname: Sharma
authors.forename: Divya
authors.initials: D
authors.lastname: Dube
authors.forename: Mau
authors.initials: M
authors.lastname: Sinha
authors.forename: Biswajit
authors.initials: B
authors.lastname: Mishra
authors.forename: Sharmistha
authors.initials: S
authors.lastname: Dey
authors.forename: Gorakh
authors.initials: G
authors.lastname: Mal
authors.forename: Krishan M L
authors.initials: KM
authors.lastname: Pathak
authors.forename: Punit
authors.initials: P
authors.lastname: Kaur
authors.forename: Sujata
authors.initials: S
authors.lastname: Sharma
authors.forename: Tej P
authors.initials: TP
authors.lastname: Singh
mesh_terms: D000117:Acetylglucosamine / Q000737:chemistry / Q000378:metabolism; D000119:Acetylmuramyl-Alanyl-Isoglutamine / Q000737:chemistry / Q000378:metabolism; D000818:Animals; D001665:Binding Sites; D002162:Camelus; D002352:Carrier Proteins / Q000737:chemistry* / Q000378:metabolism; D018360:Crystallography, X-Ray; D006801:Humans; D007113:Immunity, Innate; D008024:Ligands; D008320:Maltose / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding; D011487:Protein Conformation; D013211:Staphylococcus aureus / Q000737:chemistry*
chemical_list: D002352:Carrier Proteins; D008024:Ligands; C118897:peptidoglycan recognition protein; D000119:Acetylmuramyl-Alanyl-Isoglutamine; D008320:Maltose; D000117:Acetylglucosamine