Steve Ealick's Research Group


TenA - A Thiaminase II


PDB file:

1YAF, TenA

1YAK, TenA-HMP

*2QCX, Bacillus subtilis TenA Y112F mutant complexed with formyl aminomethyl pyrimidine )

Description:

B. subtilis TenA is a 27,267 Da protein that is not essential for growth in thiamin containing media. TenA is a thiaminase II, an enzyme that degrades thiamin to its pyrimidine and thiazole components using water as a nucleophile. The stimulation of the production of degradative enzymes by TenA at the transcriptional level is attenuated by TenI, an enzyme with a still unknown function.

The TenA monomer is a single domain, all α-helical protein consisting of 11α-helices. A deep acidic pocket is located in the central region of the protein surrounded by helices α4, α5, α9 and α10. This pocket is lined with a large number of aromatic and acidic residues and has a volume of approximately 700 Å3.


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TenA is a tetramer with 222 point symmetry and has a rectangular box shape. In the unliganded TenA structure, the four monomers of the tetramer are related by three mutually perpendicular noncrystallographic twofold axes. Each monomer makes contacts with two other monomers.

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In the liganded structure an HMP molecule is bound deep within each acidic pocket. Its binding is stabilized by a number of electrostatic and hydrogen bonding interactions.

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Reference:

Toms AV, Haas AL, Park J-H, Begley TP and Ealick SE. Structural Characterization of the Regulatory Proteins TenA and TenI from Bacillus subtilis and the identification of TenA as a Thiaminase II. Biochemistry 44:2319-2329 (2005).

*Jenkins A, Zhang Y, Ealick SE and Begley TP. Mutagenesis studies on TenA: a thiamin salvage enzyme from Bacillus subtilis. Bioorg. Chem. 36:29-32 (2008).



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