cb8b00377_si_001.pdf (1.89 MB)
Effect of Noncanonical Amino Acids on Protein–Carbohydrate Interactions: Structure, Dynamics, and Carbohydrate Affinity of a Lectin Engineered with Fluorinated Tryptophan Analogs
journal contribution
posted on 2018-05-29, 00:00 authored by Felix Tobola, Mickael Lelimousin, Annabelle Varrot, Emilie Gillon, Barbara Darnhofer, Ola Blixt, Ruth Birner-Gruenberger, Anne Imberty, Birgit WiltschiProtein–carbohydrate
interactions play crucial roles in
biology. Understanding and modifying these interactions is of major
interest for fighting many diseases. We took a synthetic biology approach
and incorporated noncanonical amino acids into a bacterial lectin
to modulate its interactions with carbohydrates. We focused on tryptophan,
which is prevalent in carbohydrate binding sites. The exchange of
the tryptophan residues with analogs fluorinated at different positions
resulted in three distinctly fluorinated variants of the lectin from Ralstonia solanacearum. We observed differences in stability
and affinity toward fucosylated glycans and rationalized them by X-ray
and modeling studies. While fluorination decreased the aromaticity
of the indole ring and, therefore, the strength of carbohydrate–aromatic
interactions, additional weak hydrogen bonds were formed between fluorine
and the ligand hydroxyl groups. Our approach opens new possibilities
to engineer carbohydrate receptors.