Erratum: I realize that I have been dismissive about the function of TrpR at around 16:00. TrpR binding is not useless. It does manage to stop the movement of RNA polymerase. The binding therefore does matter. The initial block of trpR is an important step to make the cell respond quickly to Trp availability. Think of TrpR as an immediate switch to repression state where as if you didn't have it, the switch would be slower because it takes a while to make the trp-tRNA (so the leader peptide cannot be immediately formed). Overtime, the trpR amount goes down since it represses itself. So, after a while the available trpR is lower, which affects how often the operator can be blocked by the repressor. But when it manages to bind the operator, the RNA polymerase is blocked. If the RNA polymerase is not blocked, a leader peptide is made. Thanks to one of the commenter for catching this :)
Thanks a lot for the clarification. I was searching a lot of vdos trying to find the explanation to the question I had on whether trpR is useless. I also binged a lot of ur other vdos, they're amazing. Immediate subscribe. As a ug in biotech I hope u keep em comin.
nice video man, exactly what I need for my exam:) I hope to see more videos like mRNA vaccine one, where you explain more interesting stuffs! However, keep going with your work and don't give up, you are doing amazing things, at least for those who are interested in science and molecular biology:)
It was helpful and great work, thanks. But i have a confusion about the function of TrpR repressor protein. It seems like it doesn't do anything? am i wrong or?
It is responsible for roadblocking the RNA polymerase when Trp is present in the system. Even though it does this job poorly and represses itself in the process, trpR block (weak as it may be) is actually an important step to make the cell respond quickly to Trp availability. Think of TrpR as an immediate switch to repression state vs. if you didn't have it, the switch would be slower because it takes a while to make the trp-tRNA. The binding does actually cause a reasonably strong block to RNA polymerase but overtime, this block goes away because trpR has an on/off rate at the DNA and turnover rate. Since not enough protein is made and the existing protein is turned over, the block becomes meaningless in the longterm. So, trpR is important in the beginning steps to make the transition robust. TrpR also regulates aroH operon, so saying that it doesn't do anything would be incorrect. Note that in the grand scheme of things, the bacteria is fine without a trpR - it is only a bit slower in switching between ON/OFF trp operon states, otherwise no problems. But given that trp operon is not the only place it binds, it is important for a bacteria to contain a trpR. Edit: Thanks for this question. You gave me a video idea on regulation and state transitions :)
