Effect of Noncanonical Amino Acids on Protein-Carbohydrate Interactions: Structure, Dynamics, and Carbohydrate Affinity of a Lectin Engineered with Fluorinated Tryptophan Analogs

ACS Chem Biol. 2018 Aug 17;13(8):2211-2219. doi: 10.1021/acschembio.8b00377. Epub 2018 Jun 12.


Protein-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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Proteins / chemistry
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism*
  • Crystallography, X-Ray
  • Halogenation
  • Lectins / chemistry
  • Lectins / genetics
  • Lectins / metabolism*
  • Molecular Docking Simulation
  • Polysaccharides / chemistry
  • Polysaccharides / metabolism*
  • Protein Binding
  • Protein Conformation
  • Protein Engineering
  • Ralstonia / chemistry
  • Ralstonia / genetics
  • Ralstonia / metabolism*
  • Tryptophan / analogs & derivatives*
  • Tryptophan / genetics


  • Bacterial Proteins
  • Lectins
  • Polysaccharides
  • Tryptophan