1LRJ: Crystal Structure Of E. Coli Udp-galactose 4-epimerase Complexed With Udp-n-acetylglucosamine

UDP-galactose 4-epimerase catalyzes the interconversion of UDP-Gal and UDP-Glc during normal galactose metabolism. The mammalian form of the enzyme, unlike its Escherichia coli counterpart, can also interconvert UDP-GalNAc and UDP-GlcNAc. One key feature of the epimerase reaction mechanism is the rotation of a 4-ketopyranose intermediate in the active site. By comparing the high resolution x-ray structures of both the bacterial and human forms of the enzyme, it was previously postulated that the additional activity in the human epimerase was due to replacement of the structural equivalent of Tyr-299 in the E. coli enzyme with a cysteine residue, thereby leading to a larger active site volume. To test this hypothesis, the Y299C mutant form of the E. coli enzyme was prepared and its three-dimensional structure solved as described here. Additionally, the Y299C mutant protein was assayed for activity against both UDP-Gal and UDP-GalNAc. These studies have revealed that, indeed, this simple mutation did confer UDP-GalNAc/UDP-GlcNAc converting activity to the bacterial enzyme with minimal changes in its three-dimensional structure. Specifically, although the Y299C mutation in the bacterial enzyme resulted in a loss of epimerase activity with regard to UDP-Gal by almost 5-fold, it resulted in a gain of activity against UDP-GalNAc by more than 230-fold.
PDB ID: 1LRJDownload
MMDB ID: 20265
PDB Deposition Date: 2002/5/15
Updated in MMDB: 2017/11
Experimental Method:
x-ray diffraction
Resolution: 1.9  Å
Source Organism:
Similar Structures:
Biological Unit for 1LRJ: dimeric; determined by author and by software (PISA,PQS)
Molecular Components in 1LRJ
Label Count Molecule
Proteins (2 molecules)
Udp-glucose 4-epimerase(Gene symbol: galE)
Molecule annotation
Chemicals (10 molecules)
* Click molecule labels to explore molecular sequence information.

Citing MMDB