The three-dimensional structure and recognition mechanism of Manduca sexta peptidoglycan recognition protein-1. (May 2019)

• Record Type: Journal Article
• Authors: Hu, Yingxia; Cao, Xiaolong; Li, Xiuru; Wang, Yang; Boons, Geert-Jan; Deng, Junpeng; Jiang, Haobo
• Is Part Of: Insect biochemistry and molecular biology. Volume 108(2019)
• Page Start: 44
• Page End: 52
• Publication Date: 2019-05
• Subjects: Insect immunity -- Pattern recognition -- Hemolymph protein -- Serine protease -- Prophenoloxidase activation -- Melanization; AMP antimicrobial peptide -- DAP diaminopimelate -- MBP microbe binding protein -- MPP muramyl pentapeptide -- NAM N-acetylmuramate -- PG and PGRP peptidoglycan and its recognition protein -- PO and proPO phenoloxidase and its precursor -- proHP14 hemolymph protease-14 precursor; Insect biochemistry -- Periodicals; Insects -- Physiology -- Periodicals; Insects -- Molecular aspects -- Periodicals; Biochemistry -- Periodicals; Insectes -- Biochimie -- Périodiques; Insectes -- Composition -- Périodiques; Insectes -- Physiologie -- Périodiques; Insectes -- Aspect moléculaire -- Périodiques; Biochimie -- Périodiques; Biochemistry; Insect biochemistry; Insects -- Molecular aspects; Insects -- Physiology; Periodicals; 572.8157
• DOI: 10.1016/j.ibmb.2019.03.001
• Languages: English
• ISSNs: 0965-1748

Abstract

Abstract: Peptidoglycan recognition proteins (PGRPs) recognize bacteria through their unique cell wall constituent, peptidoglycans (PGs). PGRPs are conserved from insects to mammals and all function in antibacterial defense. In the tobacco hornworm Manduca sexta, PGRP1 and microbe binding protein (MBP) interact with PGs and hemolymph protease-14 precursor (proHP14) to yield active HP14. HP14 triggers a serine protease network that produces active phenoloxidase (PO), Spätzle, and other cytokines to stimulate immune responses. PGRP1 binds preferentially to diaminopimelic acid (DAP)-PGs of Gram-negative bacteria and Gram-positive Bacillus and Clostridium species than Lys-PGs of other Gram-positive bacteria. In this study, we synthesized DAP- and Lys-muramyl pentapeptide (MPP) and monitored their associations with M. sexta PGRP1 by surface plasmon resonance. The K d values (0.57 μM for DAP-MPP and 45.6 μM for Lys-MPP) agree with the differential recognition of DAP- and Lys-PGs. To reveal its structural basis, we produced the PGRP1 in insect cells and determined its structure at a resolution of 2.1 Å. The protein adopts a fold similar to those from other PGRPs with a classical L-shaped PG-binding groove. A unique loop lining the shallow groove suggests a different ligand-binding mechanism. In summary, this study provided new insights into the PG recognition by PGRPs, a critical first step that initiates the serine protease cascade. Graphical abstract: Image 1 Highlights: Preferential binding of DAP-MPP by M. sexta PGRP1 at a k d of 0.57 μM. Determination of the PGRP1 structure at a resolution of 2.1 Å. Structure-based prediction of a zinc-independent serine hydrolase activity. Possible new mechanism for ligand binding supported by the docking analysis.