Einfluß der Temperatur auf die Transkription der T3‐DNA durch T3‐spezifische RNA‐Polymerase in zellfreien Extrakten von Escherichia coli CRT266

Abstract

AbstractCell free extracts were prepared from E. coli CRT266 9 min after infection with T3 phages. RNA synthesis in these extracts is almost entirely due to T3 RNA polymerase. The inactivation of T3 RNA polymerase in these extracts proceeds rapidly at 42 °C. 90% of the activity is lost within 10 min at this temperature. Under conditions where the formation of a stable initiation complex with T3 DNA is possible, i.e., in the presence of GTP, ATP, and UTP the T3 RNA polymerase becomes protected against heat inactivation losing only 10% of its activity during an exposure to 42 °C for 10 min. Studies on the time course of RNA synthesis have shown that reinitiation is still possible at 37 °C and 42 °C. At 44 °C, however, RNA synthesis stops abruptedly after 3 min indicating that reinitiation does no longer take place. The elongation of already initiated T3 RNA chains is rather resistant to heat. At 44 °C the same elongation rates are observed as at 37 °C and 42 °C, respectively.