Structural Characterization of the Regulatory Proteins TenA and TenI from Bacillus subtilis and Identification of TenA as a Thiaminase II

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• 作者：Angela V. Toms ; Amy L. Haas ; Joo-Heon Park ; Tadhg P. Begley ; and Steven E. Ealick
• 刊名：Biochemistry
• 出版年：2005
• 出版时间：February 22, 2005
• 年：2005
• 卷：44
• 期：7
• 页码：2319 - 2329
• 全文大小：631K
• 年卷期：v.44,no.7(February 22, 2005)
• ISSN：1520-4995

文摘

Bacillus subtilis gene products TenA and TenI have been implicated in regulating the productionof extracellular proteases, but their role in the regulation process remains unclear. The structuralcharacterization of these proteins was undertaken to help provide insight into their function. We havedetermined 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 ofthiamin by TenA likely proceeds via the same addition-elimination mechanism described for thiaminaseI. Three active-site residues, Asp44, Cys135, and Glu205, are likely involved in substrate binding andcatalysis based on the enzyme/product complex structure and the conservation of these residues withinTenA sequences. We have also determined the structure of TenI. Although TenI shows significant structuralhomology to thiamin phosphate synthase, it has no known enzymatic function. The structure suggeststhat TenI is unable to bind thiamin phosphate, largely resulting from the presence of leucine at position119, while the corresponding residue in thiamin phosphate synthase is glycine.