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4 Cards in this Set
- Front
- Back
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The path of dna and RNA in rna polymerase |
Once a transcript bubble is formed, rna polymerase holds the template and non- template strands apart. Template strand binds to rna p polymerase at the active site. The two strands are kept apart by the lid, zipper and rudder regions. Ribonucleotides(NTPs) enter the active site and base pair with the template strand |
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RNA synthesis in the rna polymerase |
Successive nucleotides are added at the 3’ end of the growing rna molecule by nucleophilic attack, forming a phosphodiester bond and releasing pyrophosphate. The 5’ end of the growing rna leaves the polymerase via and exit channel. As in DNA polymerase, two mg ions are present at the active site and catalyze the addition of nucleotides. |
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Transition from initiation to elongation |
Promoter clearance- the polymerase break away from the promoter. During promoter clearance, rna pol y undergoes a confirmational change that associates it very stable with DNA, and loosens it’s grip on imitation factors. Eukaryotic polymer is phosphorylated as it converts to the elongating complex |
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Elongation step of transcription |
Transcription is highly processive once in the elongation phase. RNA polymerase remains associated with dna and adds hundreds of thousands of bases to the growing RNA at about 20-50 nucleotides per second. The transcription bubble continues to contain 12-14 unpaired bases. RNA polymerase separates downstream dna strands, and base pairing re-forms after the RNA polymerase has passed. The most recently added ribonucleotides are within the transcription bubble |
