Table 1
Multisubunit RNAP resemble a crab claw whose 'jaws' (Figure 1, highlighted in red) interact with duplex DNA in the direction of transcription. The DNA projects along the floor the major DNA-binding channel (blue) and is secured by the RNAP 'clamp' (green) until it encounters the active centre (yellow) at the RNAP 'wall'. The DNA-RNA hybrid is perpendicular to the downstream duplex DNA and the strands are separated by the RNAP 'lid', and the transcript is guided by interactions with the RNAP 'stalk' (orange). The NTP entry pore, or secondary channel, is located under the active site and allows access of substrates and cleavage factors to the active site and extrusion of the transcript during backtracking. All RNAP subunits can be divided into three overlapping functional classes. RNAP subunits homologous to Rpo3 (corresponding to alphaI in bacteria), 10, 11 (alphaII) and 12 form the assembly platform (deep blue), whose association nucleates RNAP assembly. The two largest subunits Rpo1 (beta') and 2 (beta) form the catalytic core that harbours the active site including the Magnesium chelating carboxylate residues, the bridge and trigger helices, the downstream DNA and DNA-RNA hybrid binding sites, the secondary NTP entry channel and loop and switch regions that are instrumental in the handling of the nucleic acids scaffold including strand separation. The combination of assembly platform and catalytic core is the minimal subunit configuration of active RNAPs. The other RNAP subunits are not strictly required for basic RNAP operations (including promoter-directed transcription) and have auxiliary functions by adding interaction sites with basal transcription factors and/or nucleic acids. Rpo5 extends the RNAP jaw's interactions with the downstream duplex DNA during transcription initiation, Rpo6 (omega) aids the folding and stability of Rpo1 and acts as anchorage point for the Rpo4/7 'stalk' complex. RNAP subunits Rpo4/7 form a stable heterodimeric subcomplex, which interacts with the nascent RNA transcript during elongation and termination.
ตารางที่ 1Multisubunit RNAP resemble a crab claw whose 'jaws' (Figure 1, highlighted in red) interact with duplex DNA in the direction of transcription. The DNA projects along the floor the major DNA-binding channel (blue) and is secured by the RNAP 'clamp' (green) until it encounters the active centre (yellow) at the RNAP 'wall'. The DNA-RNA hybrid is perpendicular to the downstream duplex DNA and the strands are separated by the RNAP 'lid', and the transcript is guided by interactions with the RNAP 'stalk' (orange). The NTP entry pore, or secondary channel, is located under the active site and allows access of substrates and cleavage factors to the active site and extrusion of the transcript during backtracking. All RNAP subunits can be divided into three overlapping functional classes. RNAP subunits homologous to Rpo3 (corresponding to alphaI in bacteria), 10, 11 (alphaII) and 12 form the assembly platform (deep blue), whose association nucleates RNAP assembly. The two largest subunits Rpo1 (beta') and 2 (beta) form the catalytic core that harbours the active site including the Magnesium chelating carboxylate residues, the bridge and trigger helices, the downstream DNA and DNA-RNA hybrid binding sites, the secondary NTP entry channel and loop and switch regions that are instrumental in the handling of the nucleic acids scaffold including strand separation. The combination of assembly platform and catalytic core is the minimal subunit configuration of active RNAPs. The other RNAP subunits are not strictly required for basic RNAP operations (including promoter-directed transcription) and have auxiliary functions by adding interaction sites with basal transcription factors and/or nucleic acids. Rpo5 extends the RNAP jaw's interactions with the downstream duplex DNA during transcription initiation, Rpo6 (omega) aids the folding and stability of Rpo1 and acts as anchorage point for the Rpo4/7 'stalk' complex. RNAP subunits Rpo4/7 form a stable heterodimeric subcomplex, which interacts with the nascent RNA transcript during elongation and termination.
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