Binding of the repressor to the operator sequence blocks binding of RNA polymerase and so inhibits transcription.

TLS Online TPP Program

#Id: 813

#Unit 3. Fundamental Processes

A consensus sequence is, in each case a version of the sequence having at each position the nucleotide (or amino acid) most commonly found. consensus sequence was derived by aligning 300 sequences known to function as s70 promoters and ascertaining the most common base found at each position in the –35 and –10 hexamers.

TLS Online TPP Program

#Id: 814

#Unit 3. Fundamental Processes

Mechanism: How Polymerase Find Promoter Sequences

TLS Online TPP Program

#Id: 815

#Unit 3. Fundamental Processes

Sigma inhibits non specific binding of holoenzyme so fourth slides rapidly over non promoters sequences but binding strongly to promoters

TLS Online TPP Program

#Id: 816

#Unit 3. Fundamental Processes

Sigma factor has four binding regions over DNA. 

TLS Online TPP Program

#Id: 817

#Unit 3. Fundamental Processes

Region 2.3, 2.4, and 4.2 contact bases in the -10 and -35 elements, respectively; 

sigma factor region 1.2 contacts the promoter region just downstream from the -10 element, and region 3.0 contacts the promoter region just upstream from the -10 element.

 

TLS Online TPP Program

#Id: 818

#Unit 3. Fundamental Processes

Sigma factor Region 2.3 is responsible for melting the DNA at -10 element.