InterPro domain: IPR036652

In bacteria or archaea, YjeF N-terminal domains occur either as single proteins or fused with other domains and are commonly associated with enzymes. YjeF N-terminal domains are often fused to a YjeF C-terminal domain. It is a bifunctional enzyme that catalyses the epimerisation of the S- and R-forms of NAD(P)HX and the dehydration of the S-form of NAD(P)HX at the expense of ADP, which is converted to AMP [ 1 ].

Structurally, YjeF N-terminal domains represent a novel version of the Rossmann fold, one of the most common protein folds in nature. The YjeF N-terminal domain is comprised of a three-layer alpha-beta-alpha sandwich with a central beta-sheet surrounded by helices. This domain contains a putative catalytic site [ 2 ].

The YjeF N-terminal domain is homologous to AIBP in mammals and YNL200C in budding yeasts. AIBP and YNL200C are NAD(P)H-hydrate epimerases that catalyses the epimerisation of the S- and R-forms of NAD(P)HX, at the expense of ATP, which is converted to ADP [ 3 ].

Some proteins known to contain a YjeF N-terminal domain are listed below:

• Escherichia coli hypothetical protein YjeF.
• Thermotoga maritima hypothetical protein Tm0922.
• Yeast uncharacterised protein YNL200C.
• Yeast enhancer of mRNA-decapping protein 3 (EDC3).
• Vertebrate enhancer of mRNA-decapping protein 3 (EDC3).
• Mammalian apolipoprotein A-I binding protein (AI-BP).

1. Extremely conserved ATP- or ADP-dependent enzymatic system for nicotinamide nucleotide repair. J. Biol. Chem. 286, 41246-52
2. Novel conserved domains in proteins with predicted roles in eukaryotic cell-cycle regulation, decapping and RNA stability. BMC Genomics 5, 45