Protein recognition by cucurbit[6]uril: high affinity N-terminal complexation

Area of Science:

• Supramolecular Chemistry
• Chemical Biology
• Biophysical Chemistry

Background:

• Cucurbit[n]urils (Qn) are macrocyclic hosts widely used for protein recognition, primarily targeting N-terminal aromatic residues with Q7 and Q8.
• Cucurbit[6]uril (Q6) exhibits unique affinity for alkylamines, suggesting potential for recognizing lysine side chains, but its protein interactions are less explored.

Purpose of the Study:

• To investigate the protein complexation capabilities of cucurbit[6]uril (Q6) using Nuclear Magnetic Resonance (NMR) spectroscopy.
• To explore Q6's binding preferences beyond lysine residues and assess its potential for N-terminal recognition.

Main Methods:

• Utilized NMR spectroscopy to study interactions between Q6 and four model proteins with varying properties.
• Investigated Q6 binding to specific lysine residues (Lys) and dimethylated lysine residues.
• Engineered N-terminal methionine-lysine motifs into model proteins to assess binding affinity.

Main Results:

• Demonstrated Q6's ability to recognize specific lysine residues and N-terminal methionine-lysine motifs with high affinity (micromolar range).
• Observed similar high-affinity binding when the Met-Lys motif was engineered into a different protein.
• Provided evidence for cucurbit[8]uril (Q8) also binding to the N-terminal Met-Lys feature.

Conclusions:

• Expands the known binding repertoire of cucurbiturils, particularly highlighting Q6's capacity for N-terminal protein recognition.
• Establishes the N-terminal Met-Lys motif as a high-affinity binding site for Q6 and potentially Q8.
• Enhances the utility of cucurbiturils as versatile tools for protein sensing and molecular recognition applications.