InterPro domain: IPR013022

This entry represents a structural motif with a beta/alpha TIM barrel found in several proteins families:

• Endonuclease IV ( 3.1.21.2 ), an AP (apurinic/apyrimidinic) endonuclease that primes DNA repair synthesis by cleaving the DNA backbone 5' of AP sites [ 1 ].
• L-rhamnose isomerase ( 5.3.1.14 ), a tetramer of four TIM barrels that catalyses the isomerisation between aldoses and ketoses, such as between L-rhamnose and L-rhamnulose [ 2 ].
• Xylose isomerase ( 5.3.1.5 ), which catalyses the first reaction in the catabolism of D-xylose by converting D-xylose to D-xylulose [ 3 ].
• Mannonate dehydratase UxuA, which along with mannonate oxidoreductase converts D-fructuronate to 2-keto-3-deoxy-D-gluconate [ 4 ].

These proteins share similar, but not identical, metal-binding sites. In addition, xylose isomerase and L-rhamnose isomerase each have additional alpha-helical domains involved in tetramer formation.

1. Structure of the DNA repair enzyme endonuclease IV and its DNA complex: double-nucleotide flipping at abasic sites and three-metal-ion catalysis. Cell 98, 397-408
2. The structures of L-rhamnose isomerase from Pseudomonas stutzeri in complexes with L-rhamnose and D-allose provide insights into broad substrate specificity. J. Mol. Biol. 365, 1505-16
3. A quasi-Laue neutron crystallographic study of D-xylose isomerase. Eur. Biophys. J. 35, 601-9
4. Regulation of hexuronate system genes in Escherichia coli K-12: multiple regulation of the uxu operon by exuR and uxuR gene products. J. Bacteriol. 145, 211-20