Neelaredoxin is a 15-kDa protein that is a gene product common in anaerobic bacteria. It has superoxide-scavenging activity, and it is constitutively expressed. In addition, its expression is not further induced during its exposure to O₂ or H₂O₂ [Silva, G. et al. (2001). J. Bacteriol. 183:4413–4420]. What do the terms constitutively expressed and induced mean in terms of neelaredoxin synthesis?

Video transcript

Hi everyone. Let's look at our next question. It says the lack operandi is a classic example of an induce a Ble opera man identify the region of the lac operation where the repressor binds. So let's recall from our content video what an induce double operation is and that's one whose default state is off. So no gene transcription and something has to happen to cause the gene to be expressed. So in the case of the laC opera on it's asking us what is the region of the opera and where the repressor binds. So we have a protein called the laC repressor and it binds to choice B the operator. So the operator essentially acts as an on off switch when the laC repressor is there. The operators right next to the promoter where RNA polymerase binds. And the lac repressor being bound there physically blocks RNA preliminaries from coming in binding to the promoter and inducing transcription. So the repressor protein has to be removed for transcription to take place. So let's look at our other answer choices and understand why they're not correct choice A the promoter is not where the repressor binds. It's where RNA polymerase binds. So that actually allows transcription to take place. So it is blocked by the lac repressor. So it's part of this whole system but that's not where the repressor actually binds. So that's why it's not the correct answer. Choice C. Is the opera. And the opera refers to that the whole um unit including promoter operator and the structural genes themselves that code for the proteins that metabolize lactose. So that's not the correct answer here because we were looking for the specific binding site on the opera on where it binds and then finally, choice, either regulator and the regular later is that jean that produces the regulatory protein. So in this case the gene that produces the lack of pressure but it's not the binding site of the laC repressor, it's the gene for it itself. So that's why Choice D. Is not correct. So again, the region of the LAC opera where the repressor binds is choice be the operator. See you in the next video.