In: Biology
Describe what is meant by the term consensus sequences for transcription in E. coli and their significance in regulating transcription from promoters recognized by the σ70 factor.
Answer:-The term consensus sequences for transcription in E.coli or other prokaryotes indicates a nucleotide sequence in promotor region of transcriptional unit which is generally used to interact with σ70 factor subunit (initiation factor) of RNA polymerase holoenzyme. This promotor region has three components consisting of consensus sequence at -35 (upstream) and -10(upstream) and start site. These two consensus sequences in most E. coli promotors are essential for binding of RNA polymerase via the σ70 subunit which has crucial role in promotor recognition. Sequencing of the promotor regions among hundereds of E.coli operons have also revealed that the -35 and -10 are critical in determining the strengh of promotor. Any specific mutation in these consensus sequence can make promotor weak or strong and thus have role in regulating transcription by changing promotor binding strength with σ70 factor.