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Structure of trifunctional THI20 from yeast.
Jarrod B French1, Tadhg P Begley, Steven E Ealick
1Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853-1301, USA.
Acta Crystallographica. Section D, Biological Crystallography
|September 10, 2011
Summary
Researchers determined the crystal structure of Saccharomyces cerevisiae THI20, a trifunctional enzyme involved in thiamin salvage. The study reveals unique structural features in its thiaminase II domain, impacting its substrate hydrolysis capabilities.
Area of Science:
- Biochemistry
- Structural Biology
- Enzymology
Background:
- Thiamin salvage pathway utilizes thiaminase II to hydrolyze degradation products into 4-amino-5-hydroxymethyl-2-methylpyrimidine (HMP).
- HMP is a key intermediate in thiamin biosynthesis, phosphorylated by HMP kinase to form thiamin monophosphate.
Purpose of the Study:
- To present the crystal structure of Saccharomyces cerevisiae THI20, a trifunctional enzyme with HMP kinase and thiaminase II domains.
- To compare the structural features of THI20's domains with those of monofunctional enzymes.
Main Methods:
- X-ray crystallography was used to determine the structure of Saccharomyces cerevisiae THI20.
- Structural comparisons were made between THI20 and previously characterized monofunctional ThiD and TenA enzymes.
Main Results:
- The HMP kinase/HMP-P kinase (ThiD-like) domain of THI20 forms a dimer, similar to other ThiD enzymes.
- The thiaminase II (TenA-like) domain of THI20 forms a dimer, unlike the tetrameric form in other TenA structures.
- The TenA-like active site of THI20 exhibits unique features and possesses characteristics of two known TenA structural classes, enabling hydrolysis of thiamin and a degradation product.
Conclusions:
- The crystal structure of THI20 provides insights into the structural adaptations of a trifunctional enzyme in thiamin metabolism.
- The unique dimeric state and active site features of the TenA-like domain in THI20 contribute to its broad substrate specificity.
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