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Structure of IMPa from Pseudomonas aeruginosa in complex with an O-glycopeptide
Structural highlights
FunctionIMPA_PSEAE Protease that degrades several proteins of the host immune system. Cleaves P-selectin glycoprotein ligand-1 (PSGL-1), leading to its functional inhibition; PSGL-1 is a leukocyte cell-surface receptor essential for leukocyte recruitment to the site of infection. Next to PSGL-1, targets host CD43 and CD44 that are also involved in leukocyte homing. Thus, prevents neutrophil extravasation and thereby protects P.aeruginosa from neutrophil attack. Is also able to inhibit the decay accelerating factor (CD55), but not the cell-surface receptors CD46 and CD31.[1] Publication Abstract from PubMedThe glycosylation of proteins is typically considered as a stabilizing modification, including resistance to proteolysis. A class of peptidases, referred to as glycopeptidases or O-glycopeptidases, circumvent the protective effect of glycans against proteolysis by accommodating the glycans in their active sites as specific features of substrate recognition. IMPa from Pseudomonas aeruginosa is such an O-glycopeptidase that cleaves the peptide bond immediately preceding a site of O-glycosylation, and through this glycoprotein-degrading function contributes to the host-pathogen interaction. IMPa, however, is a relatively large multidomain protein and how its additional domains may contribute to its function remains unknown. Here, through the determination of a crystal structure of IMPa in complex with an O-glycopeptide, we reveal that the N-terminal domain of IMPa, which is classified in Pfam as IMPa_N_2, is a proline recognition domain that also shows the properties of recognizing an O-linked glycan on the serine/threonine residue following the proline. The proline is bound in the center of a bowl formed by four functionally conserved aromatic amino acid side chains while the glycan wraps around one of the tyrosine residues in the bowl to make classic aromatic ring-carbohydrate CH-pi interactions. This structural evidence provides unprecedented insight into how the ancillary domains in glycoprotein-specific peptidases can noncatalytically recognize specific glycosylated motifs that are common in mucin and mucin-like molecules. Structural evidence for a proline-specific glycopeptide recognition domain in an O-glycopeptidase.,Noach I, Boraston AB Glycobiology. 2021 May 3;31(4):385-390. doi: 10.1093/glycob/cwaa095. PMID:33030205[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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