Steve Ealick's Research Group


YaaE-A Glutaminase Implicated in Pyridoxal-5'-phosphate Biosynthesis


PDB file:

1R9G

Description:

YaaE has been identified as a PLP biosynthetic enzyme in Bacillus subtilis. It shows high sequence similarity to glutamine amidotransferase suggesting that this protein is involved in the hydrolysis of the amide of glutamine, releasing ammonia for incorporation into the pyridine ring.The incorporation is probably catalyzed by YaaD. YaaE has a high structural similarity to the histidine biosynthetic protein HisH from Thermotoga maritima.

YaaE is an α/β  three-layer sandwich containing a seven-stranded twisted mixed parallel β-sheet flanked by six α-helices on the N-terminal stretch of the sheet, four on one side and two on the other. The mixed β-sheet seems to be common to the triad amidotransferases. The asymmetric unit contains two monomers, A and B. Superimposing the monomers reveals that residues 9-14, 45-60, 87-96, and 106-115. Shown at the right is the A monomer.


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The active site crevice lies below a two-strand stretch of anti-parallel β-sheet. As in the active sites of other amidotransferases, His170 and Glu172 are separated by Pro171. A superposition with the active site of HisH shows conservation of the catalytic triad (Cys79-His170-Glu172); however, the only other conserved residue is Gly47, which is believed to contribute to the oxyanion hole.

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Reference:

Bauer JA, Bennett EM, Begley TP and Ealick SE. Three-Dimensional Structure of YaaE from Bacillus subtilis, A Glutaminase Implicated in Pyridoxal-5'-phosphate Biosynthesis. J. Biol. Chem. 279:2704-2711 (2004).



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