Polyphosphates strongly inhibit the tRNA dependent synthesis of poly(A) catalyzed by poly(A) polymerase from Saccharomyces cerevisiae |
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Authors: | Sillero María A Günther de Diego Anabel Silles Eduardo Osorio Hugo Sillero Antonio |
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Affiliation: | Departamento de Bioquímica, Instituto de Investigaciones Biomédicas Alberto Sols UAM/CSIC, Facultad de Medicina, 28029 Madrid, Spain. |
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Abstract: | Polyphosphates of different chain lengths (P3, P4, P15, P35), (1 μM) inhibited 10, 60, 90 and 100%, respectively, the primer (tRNA) dependent synthesis of poly(A) catalyzed poly(A) polymerase from Saccharomyces cerevisiae. The relative inhibition evoked by p4A and P4 (1 μM) was 40 and 60%, respectively, whereas 1 μM Ap4A was not inhibitory. P4 and P15 were assayed as inhibitors of the enzyme in the presence of (a) saturating tRNA and variable concentrations of ATP and (b) saturating ATP and variable concentrations of tRNA. In (a), P4 and P15 behaved as competitive inhibitors, with Ki values of 0.5 μM and 0.2 μM, respectively. In addition, P4 (at 1 μM) and P15 (at 0.3 μM) changed the Hill coefficient (nH) from 1 (control) to about 1.3 and 1.6, respectively. In (b), the inhibition by P4 and P15 decreased V and modified only slightly the Km values of the enzyme towards tRNA. |
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Keywords: | Poly(A) polymerase Polyphosphates Dinucleoside polyphosphates Saccharomyces cerevisiae P4 P15 |
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