Structure-functional study of PHL lectin from Photorhabdusasymbiotica

Lectins are a very important group of proteins and glycoproteins, which specifically recognize and reversibly bind glycoconjugates. Due to this interaction, lectins play a crucial role in many physiological and pathophysiological processes including immunological reactions or interactions between tissue’s cells. They also play a very important role in interactions between a pathogen and its host as they can mediate the first step of an expansion of infection. Our project is focused on study of a new lectin from the Photorhabdus asymbiotica bacterium. This bacterium is characterized as pathogen of both insects and humans. We have identified a new putative lectin (PHL) in the P. asymbiotica genome with the predicted structure similarity to the lectins from so-called AAL family, which are specific for fucosylated oligosaccharides. The AAL family contains AAL from Aleuria aurantia which inhibits a repair of epithelia or the RSL lectin from Ralstonia solanaccearum predicted as one of the key virulent factors of this plant pathogen. A wide range of methods was used for structural a functional studies of PHL. The crystal structure of PHL revealed a presence of fourteen potential binding sites per monomer. PHL belongs to seven beta-propellers, which makes this protein unique compared to proteins from AAL family, which share the six beta-propeller fold. Crystal structures of PHL with different saccharides demonstrated two types of binding sites, which could bind ligands with different polarity. PHL showed highest affinity to fucose among studied monosaccharides and binding properties of PHL will be further studied with more complex saccharides.