Regulatory mechanisms differ in UMP kinases from gram-negative and gram-positive bacteria
| Autor: | Adrian Onu, Octavian Bârzu, Monica Straut, Anne-Marie Gilles, Nicolae Palibroda, Nadia Bucurenci, Cécile Evrin, Neli Slavova-Azmanova, Liliane Assairi, Mihaela Ileana Ionescu |
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| Rok vydání: | 2007 |
| Předmět: |
GTP'
Allosteric regulation Molecular Sequence Data Cooperativity Uridine Triphosphate Gram-Positive Bacteria Biochemistry Catalysis Adenosine Triphosphate Gram-Negative Bacteria heterocyclic compounds Nucleotide Amino Acid Sequence Molecular Biology chemistry.chemical_classification Binding Sites biology Kinase Cell Biology biology.organism_classification Enzyme Activation A-site Enzyme chemistry Mutagenesis Site-Directed Guanosine Triphosphate Nucleoside-Phosphate Kinase Uridine Monophosphate Bacteria |
| Zdroj: | The Journal of biological chemistry. 282(10) |
| ISSN: | 0021-9258 |
| Popis: | In this work, we examined the regulation by GTP and UTP of the UMP kinases from eight bacterial species. The enzyme from Gram-positive organisms exhibited cooperative kinetics with ATP as substrate. GTP decreased this cooperativity and increased the affinity for ATP. UTP had the opposite effect, as it decreased the enzyme affinity for ATP. The nucleotide analogs 5-bromo-UTP and 5-iodo-UTP were 5–10 times stronger inhibitors than the parent compound. On the other hand, UMP kinases from the Gram-negative organisms did not show cooperativity in substrate binding and catalysis. Activation by GTP resulted mainly from the reversal of inhibition caused by excess UMP, and inhibition by UTP was accompanied by a strong increase in the apparent Km for UMP. Altogether, these results indicate that, depending on the bacteria considered, GTP and UTP interact with different enzyme recognition sites. In Gram-positive bacteria, GTP and UTP bind to a single site or largely overlapping sites, shifting the T ⇄ R equilibrium to either the R or T form, a scenario corresponding to almost all regulatory proteins, commonly called K systems. In Gram-negative organisms, the GTP-binding site corresponds to the unique allosteric site of the Gram-positive bacteria. In contrast, UTP interacts cooperatively with a site that overlaps the catalytic center, i.e. the UMP-binding site and part of the ATP-binding site. These characteristics make UTP an original regulator of UMP kinases from Gram-negative organisms, beyond the common scheme of allosteric control. |
| Databáze: | OpenAIRE |
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