Figure 3From: Bridge helix and trigger loop perturbations generate superactive RNA polymerasesA functional interaction between the Q823 and R829 positions. (a) Model of the T. thermophilus bridge helix kink (PDB 1IW7). The interacting residues (β' D1090 and R1096) are shown as space-filling models and the surrounding helix in green in ribbon representation. Note that the flipped-out D1090 residue juxtaposes its side chain opposite R1096. The resulting contact stabilizes the kinked α helix. (b) High-throughput transcription assay results of mjA' R829X substitutions. The results are shown relative to wild-type activity (100%; dashed line). Single substitution mutant results are shown in dark blue with the substituted residues shown along the x-axis positions; note that all substitutions, except K, result in a substantial drop of catalytic activity. The results of two double mutant constructs, Q823R/R829D (R-D) and Q823H/R829D (H-D), are shown on the same scale as a separate graph with green bars. Error bars indicate standard deviation (n = 4). (c) Abortive and elongation transcription assay results of the double mutants. Q823R/R829D is inactive; Q823H/R829D has 49% (abortive assay) and 52% (elongation assay) of wild-type activity.Back to article page