T7 RNA Polymerase is a DNA-dependent RNA polymerase that has a high specificity for bacteriophage T7 promoter sequences. The enzyme synthesizes large quantities of RNA from DNA inserted into a transcription vector downstream from a T7 promoter. A T7 RNA Polymerase technical bulletin is available. Application: Synthesis of labeled and unlabeled RNA transcripts (1). Source: Purified from E. coli expressing the T7 RNA Polymerase gene on a plasmid. Performance and Quality Testing: 3´ and 5´ exodeoxyribonuclease, ribonuclease, and DNA nicking assays; performance in a transcription reaction. Unit Definition: One unit hydrolyzes 1 nmol of ribonucleotide into acid-precipitable material in 1 h at 37°C using a T7 transcription vector as template. Unit Reaction Conditions: 40 mM Tris-HCl (pH 8.0), 25 mM NaCl, 8 mM MgCl2 , 2 mM spermidine-(HCl)3 , 5 mM DTT, 0.4 mM ATP, 0.4 mM CTP, 0.4 mM GTP, 0.4 mM UTP, 1 µCi [3H]GTP, 1 µg Sph I-cut pT7L13, and enzyme in 50 µl for 10 min. at 37°C.