Crystal structure of Legionella pneumophila glycosidase effector LegY

Legionella pneumophila translocates approximately 330 effectors into host cells via its type IVB secretion system. These effectors mediate a diverse array of post-translational modifications, among which reversible glycosylation is closely associated with bacterial virulence. Although several glycosyltransferase effectors have been identified that glycosylate host proteins to subvert host cellular processes, no glycosidase effector has been reported to date. Here, we report the crystal structure of LegY, a putative glycosidase effector from L. pneumophila, determined to 1.46 Å resolution (PDB entry 27xj). LegY adopts a single-domain (α/α)₆-barrel fold and is structurally assigned as a member of glycoside hydrolase family 15 (GH15). LegY structurally shows high similarity to fungal glucoamylases but shares lower homology with known prokaryotic counterparts. Phylogenetic analysis clusters LegY within the fungal clade, suggesting possible horizontal gene transfer or convergent evolution. This study provides structural insights into LegY, laying a foundation for future uncovering of its putative function during L. pneumophila infection.