title: Structural characterization of the regulatory proteins TenA and TenI from Bacillus subtilis and identification of TenA as a thiaminase II.
abstract: Bacillus subtilis gene products TenA and TenI have been implicated in regulating the production of extracellular proteases, but their role in the regulation process remains unclear. The structural characterization of these proteins was undertaken to help provide insight into their function. We have determined the structure of TenA alone and in complex with 4-amino-2-methyl-5-hydroxymethylpyrimidine, and we demonstrate that TenA is a thiaminase II. The TenA structure suggests that the degradation of thiamin by TenA likely proceeds via the same addition-elimination mechanism described for thiaminase I. Three active-site residues, Asp44, Cys135, and Glu205, are likely involved in substrate binding and catalysis based on the enzyme/product complex structure and the conservation of these residues within TenA sequences. We have also determined the structure of TenI. Although TenI shows significant structural homology to thiamin phosphate synthase, it has no known enzymatic function. The structure suggests that TenI is unable to bind thiamin phosphate, largely resulting from the presence of leucine at position 119, while the corresponding residue in thiamin phosphate synthase is glycine.
authors.affiliation: Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, USA.
authors.forename: Angela V
authors.initials: AV
authors.lastname: Toms
authors.forename: Amy L
authors.initials: AL
authors.lastname: Haas
authors.forename: Joo-Heon
authors.initials: JH
authors.lastname: Park
authors.forename: Tadhg P
authors.initials: TP
authors.lastname: Begley
authors.forename: Steven E
authors.initials: SE
authors.lastname: Ealick
mesh_terms: D019883:Alkyl and Aryl Transferases / Q000737:chemistry; D001412:Bacillus subtilis / Q000737:chemistry* / Q000201:enzymology*; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism*; D001665:Binding Sites; D003460:Crystallization; D018360:Crystallography, X-Ray; D019281:Dimerization; D006867:Hydrolases / Q000737:chemistry* / Q000378:metabolism; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D011743:Pyrimidines / Q000378:metabolism; D012097:Repressor Proteins / Q000737:chemistry* / Q000378:metabolism; D013431:Sulfates / Q000378:metabolism; D013838:Thiamine Triphosphate / Q000737:chemistry / Q000378:metabolism; D015534:Trans-Activators / Q000737:chemistry* / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D011743:Pyrimidines; D012097:Repressor Proteins; D013431:Sulfates; D015534:Trans-Activators; D013838:Thiamine Triphosphate; C032260:4-amino-5-hydroxymethylpyrimidine; D019883:Alkyl and Aryl Transferases; C435495:thiamin phosphate synthase; D006867:Hydrolases; C022731:thiaminase II