Structural Determinants for Substrate Binding and Catalysis in Triphosphate Tunnel Metalloenzymes
| Autor: | Vincent Truffault, Michael Hothorn, Jacobo Martinez |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2015 |
| Předmět: |
Stereochemistry
nuclear magnetic resonance (NMR) Arabidopsis Plant Biology Biochemistry Enzyme catalysis Evolution Molecular 03 medical and health sciences chemistry.chemical_compound Thiamine triphosphatase Protein structure adenylate cyclase (adenylyl cyclase) Hydrolase Metalloproteins Escherichia coli enzyme mechanism Binding site protein structure Molecular Biology x-ray crystallography 030304 developmental biology chemistry.chemical_classification 0303 health sciences inorganic polyphosphatase Chemistry Arabidopsis Proteins Escherichia coli Proteins 030302 biochemistry & molecular biology Cell Biology Inorganic Pyrophosphatase Enzyme ddc:580 Structural Homology Protein manganese thiamine triphosphatase Thiamine triphosphate Adenosine triphosphate human activities |
| Zdroj: | Journal of Biological Chemistry, Vol. 290, No 38 (2015) pp. 23348-23360 The Journal of Biological Chemistry |
| ISSN: | 0021-9258 |
| Popis: | Background: Triphosphate tunnel metalloenzymes carry out diverse enzymatic reactions. Results: Two metal co-factors are identified involved in substrate binding and in catalysis. Conclusion: A unified catalytic mechanism is proposed and biochemically investigated. Significance: The functional diversity of TTM enzymes is rationalized by a common mechanism that allows very different substrates to be bound and processed. Triphosphate tunnel metalloenzymes (TTMs) are present in all kingdoms of life and catalyze diverse enzymatic reactions such as mRNA capping, the cyclization of adenosine triphosphate, the hydrolysis of thiamine triphosphate, and the synthesis and breakdown of inorganic polyphosphates. TTMs have an unusual tunnel domain fold that harbors substrate- and metal co-factor binding sites. It is presently poorly understood how TTMs specifically sense different triphosphate-containing substrates and how catalysis occurs in the tunnel center. Here we describe substrate-bound structures of inorganic polyphosphatases from Arabidopsis and Escherichia coli, which reveal an unorthodox yet conserved mode of triphosphate and metal co-factor binding. We identify two metal binding sites in these enzymes, with one co-factor involved in substrate coordination and the other in catalysis. Structural comparisons with a substrate- and product-bound mammalian thiamine triphosphatase and with previously reported structures of mRNA capping enzymes, adenylate cyclases, and polyphosphate polymerases suggest that directionality of substrate binding defines TTM catalytic activity. Our work provides insight into the evolution and functional diversification of an ancient enzyme family. |
| Databáze: | OpenAIRE |
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