Comparative Study of Cyanobacterial and E. coli RNA Polymerases: Misincorporation, Abortive Transcription, and Dependence on Divalent Cations
Figure 2
Transcription from the T7A1 and the psbA2 promoters by cyanobacterial and E. coli RNAPs as well as their chimeric enzymes. (a) The DNA sequences of the T7A1 and the psbA2 promoters. The putative −10 and −35 elements are underlined, and the transcribed sequences are indicated in uppercase letters. (b) The analysis of transcripts labeled with [γ-32P]ATP from the T7A1 promoter with 20% polyacrylamide in the presence of 7M urea in TBE buffer. (c) The transcripts from the psbA2 promoter. The round of transcription is indicated at the top of the gels. The runoff and abortive transcripts are indicated by arrowheads and parentheses, respectively. The length and the incorporated nucleotide at its 3′ end of an abortive transcript are indicated on the left margin. Asterisks indicate the abortive transcripts involving misincorporation. The radioactive contaminants that is contained in [γ-32P]ATP are also indicated in lane 17. (d) The amounts of the run-off transcript normalized by that of the intact E. coli enzymes (red) and the ratio of the amount of abortive transcripts to that of the run-off transcript in logarithmic scale.
