Perception of MAMPs or DAMPs by cell surface PRRs initiates a localized basal defense response called MAMP triggered immunity which inhibits the growth and activity of nonadapted pathogens or pests.

TLS Online TPP Program

#Id: 6284

#Unit 3. Fundamental Processes

Mechanism: How Polymerase Find Promoter Sequences

TLS Online TPP Program

#Id: 6285

#Unit 3. Fundamental Processes

TLS Online TPP Program

#Id: 6286

#Unit 3. Fundamental Processes

The overall reaction rate for the bacterial RNA polymerase can be as fast as 40–50 nucleotides/ second at 37°C for most transcripts; this is about the same as the rate of translation (15 amino acids/sec), but much slower than the rate of DNA replication (800 bp/sec).

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#Unit 3. Fundamental Processes

As RNA polymerase moves along the DNA template, it unwinds the duplex at the front of the bubble (the unwinding point), and the DNA  automatically reforms the double helix at the back (the rewinding point).  The length of thetranscription bubble is 12 to 14 bp, but the length of the RNA–DNA hybrid within the bubble is only 8 to 9 bp. As the enzyme moves along the template, the DNA duplex reforms, and the RNA is displaced as a free polynucleotide chain The last 14 ribonucleotides in the growing RNA are complexed with the DNA and/or the enzyme at any given moment.

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#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 there in different examples. Thus, the consensus sequence for promoters in E. coli recognized by RNA polymerase containing s70

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#Id: 6289

#Unit 3. Fundamental Processes

This 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. That nucleotide is then chosen as the nucleotide of choice at that position in the consensus; its relative frequency and the frequencies with which the other three nucleotides occur at each position are portrayed in the graph. 

Note that there is no significant consensus among the 17–19 nucleotides that lie in the region between –35 and –10.