| Autor: |
Zaychikov, Evgeny, Denissova, Ludmilla, Meier, Thomas, Götte, Matthias, Heumann, Hermann |
| Zdroj: |
Journal of Biological Chemistry; January 1997, Vol. 272 Issue: 4 p2259-2267, 9p |
| Abstrakt: |
The transcription bubble formed in the binding complex of T7A1 promoter upon Escherichia coliRNA polymerase was analyzed by chemical probes, namely by single-strand specific reagents, to map the unpaired bases in the bubble, and by FeEDTA, to analyze the accessibility of the DNA backbone. The latter probe could also be used as a local hydroxyl radical probe placed close to the Mg2+-binding site in the active center. The data show that the transcription bubble consists of two parts, an Mg2+-dependent part and an Mg2+-independent part, both having individual transition temperatures. The data further suggest that formation of a transcription active open complex is preceded by a transition state complex having enhanced affinity for those Mg2+ions presumably participating in the formation of the catalytic site. Our data also suggests that the three catalytically active Mg2+ions in RNA polymerase are functionally not equivalent. One/two of the three Mg2+ions are responsible for the polymerization, the other two/one for enlargement of the transcription bubble. |
| Databáze: |
Supplemental Index |
| Externí odkaz: |
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