Heptabladed Beta-Propeller Lectins Pll2 And Phl From Photorhabdus Spp. Recognize O Methylated Sugars And Influence The Host Immune System

O-methylation is an unusual sugar modification with a function that is not fully understood. Given its occurrence and recognition by lectins involved in the immune response, methylated sugars were proposed to represent a conserved pathogen-associated molecular pattern. We describe the interaction ofO-methylated saccharides with two beta-propeller lectins, the newly described PLL2 from the entomopathogenic bacteriumPhotorhabdus laumondii, and its homologue PHL from the related human pathogenPhotorhabdus asymbiotica. The crystal structures of PLL2 and PHL revealed up to 10 out of 14 potential binding sites per protein subunit to be occupied withO-methylated structures. The avidity effect strengthens the interaction by 4 orders of magnitude. PLL2 and PHL also interfere with the early immune response by modulating the production of reactive oxygen species and phenoloxidase activity. Since bacteria fromPhotorhabdusspp. have a complex life cycle involving pathogenicity towards different hosts, the involvement of PLL2 and PHL might contribute to the pathogen overcoming insect and human immune system defences in the early stages of infection. Databases Structural data are available in PDB database under the accession numbers , , , , , , , and .