Structural characterization of a mannose-binding protein-trimannoside complex using residual dipolar couplings

Area of Science:

• Biochemistry
• Structural Biology
• Nuclear Magnetic Resonance (NMR) Spectroscopy

Background:

• Mannose-binding protein (MBP) plays a crucial role in the innate immune system.
• Understanding MBP's ligand-binding properties is essential for elucidating its biological functions.

Purpose of the Study:

• To investigate the ligand-binding properties of a 53 kDa homomultimeric trimer from mannose-binding protein (MBP).
• To determine the structural basis of MBP-oligosaccharide interactions.

Main Methods:

• Utilized residual dipolar couplings (RDCs) measured from NMR spectra of isotopically labeled MBP and a trisaccharide ligand.
• Determined an order tensor for MBP using 1H-15N backbone amide NMR assignments and RDC measurements.
• Measured 13C-1H couplings for the bound trimannoside ligand at natural abundance.

Main Results:

• An order tensor for MBP was determined, consistent with symmetry-based predictions.
• Orientational constraints from RDC measurements were used to dock the trimannoside ligand into the MBP binding site.
• A structural model for MBP-oligosaccharide interactions was generated.

Conclusions:

• NMR-based RDC measurements provide valuable orientational information for studying protein-ligand interactions.
• The generated structural model offers insights into the molecular recognition mechanisms of MBP.
• This study demonstrates the utility of RDCs in characterizing the structure and dynamics of protein-ligand complexes.