Proofreading e. coli rna polymerase synthesizes rna with remarkable fidelity in vivo. its low error rate may be achieved, in part, by a proofreading mechanism f

Proofreading E. coli RNA polymerase synthesizes RNA with remarkable fidelity in vivo. Its low error rate may be achieved, in part, by a proofreading mechanism found in DNA polyrmerases similar to that found in DNA polymerase proofreading involves two key events. The first event is a short backtracking motion of the enzyme along the DNA template through several base pairs. The movement is directed upstream in the opposite direction to transcriptional elongation (3' 5). DNA Cleaved3 RNA Elongating RNAP Back-tracted RNAP (S RNA The second event is nucleolytic cleavage, which occurs after a variable "pause" of the polymerase his delay can last anywhere from 20 seconds to 30 minutes in vitro. In its backtracked state, the olymerase can cleave off and discard the most recently added base(s) by nuclease activity. In this Ocess, a new 3 end is generated at the active site, ready for subsequent polymerization onto the ascent RNA chain. Edunde.com

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Simran Babbar

what is actually backtracking?
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Krishan k jakhad

RNA polymerase (abbreviated RNAP or RNApol, and officially DNA-directed (dependent) RNA polymerase), is an enzyme that synthesizes RNA from a DNA template. Unlike the proofreading mechanisms of DNA polymerase those of RNAP have only recently been investigated. Proofreading begins with separation of the mis-incorporated nucleotide from the DNA template. This pauses transcription. The polymerase then backtracks by one position and cleaves the dinucleotide that contains the mismatched nucleotide. In the RNA polymerase this occurs at the same active site used for polymerization and is therefore markedly different from the DNA polymerase where proofreading occurs at a distinct nuclease active site. The overall error rate is around 10−4 to 10−6
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the mechanism is different ...it is not the same as given in eduncle text that is a typing mistake alright. . In the RNA polymerase this occurs at the same active site used for polymerization and is therefore markedly different from the DNA polymerase where proofreading occurs at a distinct nuclease active site.
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