rrnB T1 and T2 terminator

The termination region of the rrnB gene coding for ribosomal RNA in Escherichia coli is large and complex. It contains two regions (T1 and T2) with typical factor-independent terminator-like sequences, two additional inverted repeats (lR1 and IR2) and a pair of direct repeats. The whole region is frequently employed as an efficient terminator of transcription in several cloning vectors. In the pDONR vector series it protects the cloned gene from expression by vector-encoded promoters, thereby reducing possible toxicity. The rrnB T1 T2 region was shown to be an efficient terminator by Orosz et al. (1991).