The structure of Escherichia coli core RNA polymerase (RNAP) complexed with the transcript cleavage factor GreB was determined from electron micrographs of negatively stained, flattened helical crystals. A binding assay was developed to establish that GreB was incorporated into the RNA polymerase crystals with high occupancy through interactions between the globular C-terminal domain and the RNA polymerase. Comparison of the core RNAP:GreB structure with the previously determined structure of core RNAP located the GreB binding site on one face of the RNA polymerase, next to but not in the 25 Å-diameter channel of RNA polymerase.
- E. coli RNA polymerase
- Electron microscopy
- Transcript cleavage factor
- Transcription elongation factor
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