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Updated: Jun 22, 2026

Determination of Protein-ligand Interactions Using Differential Scanning Fluorimetry
Published on: September 13, 2014
Ligand binding and substrate discrimination by UDP-galactopyranose mutase
Todd D Gruber1, M Jack Borrok, William M Westler
1Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706-1544, USA.
UDP-galactopyranose mutase (UGM) is essential for pathogenic microbes. We determined the first UGM-ligand complex structure, revealing insights into its catalytic mechanism and substrate selectivity for UDP-Galp and UDP-Galf.
Area of Science:
- Biochemistry
- Structural Biology
- Microbiology
Background:
- Galactofuranose (Galf) is a key component in the cell walls of many pathogenic microbes.
- UDP-galactopyranose mutase (UGM) is crucial for synthesizing the Galf precursor, UDP-Galf, making it essential for pathogen viability.
Purpose of the Study:
- To elucidate the catalytic mechanism and substrate selectivity of UGM.
- To obtain structural data of an enzyme-substrate complex, which was previously lacking.
Main Methods:
- X-ray crystallography was used to determine the structure of UGM from Klebsiella pneumoniae bound to UDP-glucose (UDP-Glc).
- Saturation transfer difference NMR was employed to compare the binding orientations of UDP-Galp and UDP-Glc.
Main Results:
- The first structure of a UGM-ligand complex (UGM-UDP-Glc) was solved at 2.5 A resolution.
- Structural data revealed that while the uridine moiety binds similarly for UDP-Galp and UDP-Glc, the sugar moieties adopt different orientations.
- The UDP-Glc orientation disfavors covalent catalysis, consistent with UDP-Glc not being a substrate.
Conclusions:
- The study provides critical insights into the catalytic mechanism and substrate discrimination of UGM.
- The findings highlight the molecular basis for UGM's preference for UDP-Galp over other UDP sugars, offering potential targets for antimicrobial drug development.
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