Splice sites are directional in nature. 5’ splice site -the left, or donor, site and the 3’ splice site - right, or acceptor, site.

TLS Online TPP Program

#Id: 2303

#Unit 3. Fundamental Processes

Mechanism: How Polymerase Find Promoter Sequences

TLS Online TPP Program

#Id: 2304

#Unit 3. Fundamental Processes

Amino acids in the 2.4 a-helix of beta70 contact specific bases in the coding strand of the -10 promoter sequences.

TLS Online TPP Program

#Id: 2305

#Unit 3. Fundamental Processes

Initiation complex contains sigma and covers 75bp

TLS Online TPP Program

#Id: 2306

#Unit 3. Fundamental Processes

Initiation elongation complex forms at 10 bases, mayloses sigma, and loses contacts from -35 to -55.

TLS Online TPP Program

#Id: 2307

#Unit 3. Fundamental Processes

During the transition to the open complex, the conformation of both the RNA polymerase and the DNA change. 

1) 90° bend in the DNA, which allows the template strand to approach the active site of the enzyme; 

2) strand opening of the promoter DNA between -11 and +3 with respect to the transcription start site; 

3) the promoter DNA scrunches into the active channel forming the transcription bubble; and 

4) closing of the jaws of the enzyme to encircle the section of the promoter downstream section of the transcription start site.

TLS Online TPP Program

#Id: 2308

#Unit 3. Fundamental Processes

Sigma factor contacts the promoter directly at both the -35 and -10 consensus sequences was provided by substitutions in the sigma factor that suppressed mutations in the consensus sequences.