El alelo mutante nrdA101 codifica una NDP reductasa (única enzima requerida directamente para la biosíntesis de los precursores del DNA) que in vitro se inactiva en 2 minutos a 42°C. Sin embargo, un mutante nrdA101 tiene capacidad para sintetizar DNA a 42ºC en presencia de rifampicina durante 150 minutos. En este trabajo se ha determinado la causa de esta síntesis de DNA a temperatura restrictiva y se ha demostrado que la NDP reductasa es degradada por una proteasa sintetizada a 42°C en el mutante nrdA101. Los resultados obtenidos sugieren que la NDP reductasa se encuentra incluida en la hiperestructura de replicación.
The nrdA101 mutant allele codes for an NDP reductase (the only specific enzyme required for the enzymatic synthesis of the precursors of DNA) which is inactivated in 2 minutes at 42°C in vitro. However, an nrdA101 mutant strain is able to synthesize DNA at 42ºC during 150 minutes in presence of rifampicin. In this work we have determined the cause of this synthesis at restrictive temperature and we have proved that NDP reductase is degraded by a protease synthesized at 42°C in the nrdA101 mutant. The results obtained suggest that NDP reductase is included in the replication hyperstructure.
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