Structural similarity of YbeD protein from Escherichia coli to allosteric regulatory domains

Lipoic acid is an essential prosthetic group in several metabolic pathways. The biosynthetic pathway of protein lipoylation in Escherichia coli involves gene products of the lip operon. YbeD is a conserved bacterial protein located in the dacA-lipB intergenic region. Here, we report the nuclear magnetic resonance structure of YbeD from E. coli. The structure includes a betaalphabetabetaalphabeta fold with two alpha-helices on one side of a four-strand antiparallel P-sheet. The beta2-beta3 loop shows the highest sequence conservation and is likely functionally important. The P-sheet surface contains a patch of conserved hydrophobic residues, suggesting a role in protein-protein interactions. YbeD shows striking structural homology to the regulatory domain from D-3-phosphoglycerate dehydrogenase, hinting at a role in the allosteric regulation of lipoic acid biosynthesis or the glycine cleavage system.