N‑Terminal Protein Complexation and Assembly with a Triangular Sulfated Macrocycle.

Area of Science:

• Structural biology
• Biochemistry
• Crystallography

Background:

• Ralstonia solanacearum lectin (RSL) is a protein with potential roles in molecular interactions.
• Sulfated macrocycles are emerging as novel molecules with unique binding properties.
• Understanding protein-ligand interactions is crucial for biochemistry and structural biology.

Purpose of the Study:

• To elucidate the structural basis of RSL interaction with a novel sulfated macrocycle, STP3.
• To explore the protein-binding modes and implications for crystal packing.
• To investigate potential applications in protein assembly and understanding lectin-heparan sulfate interactions.

Main Methods:

• X-ray crystallography was used to determine two cocrystal structures of mutant RSL with STP3.
• Analysis of the crystal structures revealed specific binding interactions and their effect on crystal packing.

Main Results:

• Two distinct binding modes of STP3 to RSL were identified: methionine encapsulation and insertion between surface loops.
• The rigidity of the STP3 macrocycle was observed to facilitate crystal packing.
• The observed interactions provide a structural basis for understanding lectin-macrocycle complex formation.

Conclusions:

• The study presents novel cocrystal structures of RSL with STP3, detailing unique binding interactions.
• STP3 demonstrates potential as a tool for protein assembly and crystallization.
• The findings have implications for understanding lectin-heparan sulfate interactions in biological systems.