69-kDa and 100-kDa Isoforms of Interferon-Induced (2'-5')Oligoadenylate Synthetase Exhibit Differential Catalytic Parameters
| Autor: | Julià Blanco, Ara G. Hovanessian, Dominique Rebouillat, Isabelle Marié |
|---|---|
| Rok vydání: | 1997 |
| Předmět: | |
| Zdroj: | Scopus-Elsevier |
| ISSN: | 1432-1033 0014-2956 |
| Popis: | The (2′-5′)oligoadenylate synthetase represents a family of interferon-induced proteins which when activated by double-stranded (ds)RNA polymerizes ATP into 2′-5′-linked oligomers with the general formula pppA(2′p5′A)n, where n > 1, which for convenience are referred to as 2–5A. We studied here the influence of pH, dsRNA concentration and time on oligomeric composition of 2–5A synthesized by purified 69-kDa and 100-kDa isoforms of (2′-5′)oligo(adenylate) synthetase. In optimal conditions for activity, the 69-kDa form synthesized higher oligomers of 2–5A molecules whereas the 100 kDa form synthesized preferentially dimeric molecules, which are known not to be functional for the activation of RNase L. This difference does not reflect a differential affinity of the enzymes for the preformed 2–5A dimer, which is found to be a very poor substrate for both enzymes. This latter strongly suggests that the mechanism of elongation is more likely processive. Moreover, we show that both isoforms have efficient nucleotidyl-transferase activity and provide evidence that, in optimized conditions, GTP can be used alone as substrate by these enzymes to generate pppG2′p5′G. Our results clearly demonstrate that the 69-kDa and 100-kDa forms of (2′–5′)oligoadenylate synthetase manifest various differential catalytic activities, and favor the hypothesis that these enzymes might have other functions in the cell besides those in the 2-5A system. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|