| Primary Identifier | IPR006358 | Type | Family |
| Short Name | Tscrpt_elong_fac_GreB |
| description | Bacterial GreA and GreB promote transcription elongation by stimulating an endogenous, endonucleolytictranscript cleavage activity of the RNA polymerase, allowing RNA transcription to continue past template-encoded arresting sites. GreA and GreB are sequence homologues and have homologues inevery known bacterial genome. GreA and GreB stimulate transcriptcleavage in different ways; GreA induces cleavage of 3'-RNA fragments 2-3 nt in length and can only preventthe formation of arrested complexes, whereas GreB induces cleavage of fragments up to 18 nt in length and canrescue preexisting arrested complexes [].A 15 Angstrom resolution helical reconstruction of the Escherichia coli core RNA polymerase (RNAP)/GreB complex that allows fitting of high-resolution RNAP andGreB structures. The model of the complex reveals a remarkable binding mode for GreB; the globular C-terminal domain binds RNAP at the edge of the active site channel, while the N-terminal coiled-coil domain extends 45 Angstrom into a channel directly to theRNAP active site. The results point to a key role for conserved acidic residues at the tip of the Gre factor coiled coil in modifying the RNAP active site to catalyse the transcript cleavage reaction, and mutational studies confirm that these positions are critical for Gre factor function. Functional differences between GreA and GreB correlate with the distribution of positively charged residues on one face of the N-terminal coiledcoil. |
