Oh in the series of videos we have been discussing about the proteins and enzymes in prokaryotic and eukaryotic transcription now in this video we'll be discussing about the mechanism of prokaryotic transcription the prokaryotic transcription proceeds in three steps initiation elongation and termination and this process is driven by DNA dependent RNA polymerase enzyme which transcribes the DNA the RNA polymerase is a core enzyme which is having different subunits it has got alpha beta beta Prime and Omega subunits the alpha subunit is further divided into 2 4 the subunits alpha 1 and alpha 2 subunit moreover for
this enzyme to work we have Sigma factors and Ecola has 7 different Sigma factors like it has got Sigma 70 Sigma 54 38:32 28 24 and 18 the Sigma 70 is called the housekeeping Sigma factor since it's involved in the transcription of all major genes rest of the Sigma factors have been shown in the table which transcribes the following genes like we have Sigma 32 it transcribes the heat shock genes during stress now let's jump towards the prokaryotic promoter first it has got RNA startpoint while from the transcription starts there is the plus 1 position
then it has got minus 10 region called the Pribnow box followed by - 35 region and prokaryotes also have up element as shown in the diagram the minus 10 region has consensus sequence as d 8080 while as minus 35 region has got T TGA CA sequence and to these regions of promoter the RNA polymerase binds the table shown here has listed different promoters in e.coli of different genes if you look at the functions of these elements on promoter we see - 10 region that's the problem box it has got the function of transcription initiation then
were the minus 35 region it has only the function of transcription that means it goes in the transcription rate during the prokaryotic transcription then we have the up element it shows interaction with alpha CTD domain or polymerase enzyme so these are the different functions of these elements now let's see the transcription process in detail in this diagram we have a DNA molecule having promoter and start point shown and we also have RNA polymerase and Sigma factor separately when the transcription is to begin the Sigma factor combines with RNA polymerase enzyme first and renders it into
its active form called the hollow enzyme now this hollow enzyme this active form of RNA polymerase recognizes the promoter on DNA and binds to it and first of all it causes unwinding a transcription start point which gives us the open complex form of DNA from here the transcription initiation kicks in well first of all the polymerase tries to initiate the process but fails to do so so we call it about to initiation because the polymerase is not able to go beyond the threshold a nucleotide number which is approximately 10 nucleotides but once polymerase stabilizes and
is able to go beyond threshold 10 nucleotides so that way we call that successful incision so from here the elongation mode starts where the nucleotides are added to the RNA transcript now we see the polymerase orientation also metals here because we know polymerase synthesized RNA transcript in five prime to three prime direction so RNA polymerase that moves from left to right makes RNA by using the bottom strand as templates train and polymerase that moves from right to left uses a per strand as a template strand and synthesizes RNA molecule for this concludes the transcription initiation
plus elongation and it's termination will be disgusted in their next video I hope you liked the video if you liked it give it a thumbs up do consider supporting me back on patreon and also make sure subscribe this channel Thanks
