Describe the structure of RNA polymerase in bacteria. What is the core enzyme? What is the role of the σ subunit?

Video transcript

Welcome back. Here's our next problem in bacteria. The sigma factors bind with the core RNA polymerase forming the hollow enzyme after the initiation of transcription, the factor unbind and the core enzyme starts to catalyze the reaction, forming a blank structure with the internal channel. So here we're talking about how RNA polymerase um carries out transcription in pro carry outs. They don't have a nucleus, It happens in cytoplasm and unlike you carry outs, bacteria just have a single RNA pollen race. So this is asking us about the structure that the RNA polymerase forms. So to help us recall the nature of that shape of that structure, just put up a nice little diagram here of that are in a race one. You see we have the sigma factor here and then all the sub units of R. RNA polymerase one, we've got two alpha subunits and omega sub unit very small there and then a beta and beta prime sub unit. We see that the D. N. A coding strand gets fed into this channel here while the D. N. A complementary strand goes out around the outside here. And it's pretty clear looking at the structure that this shape is logically called choice D the crab claw as that's very clearly what it resembles. So when we look at our other answer choices it's obviously not a spider web shape or a horseshoe choice B. Um The RNA polymerase to in you carry outs uh combines transcription factors and the transcription factors do have a horseshoe shaped horseshoe shape shape. If you associate that with an RNA polymerase but not in pro carry outs, and then Choice C. Hairpin loop. Again, this phrase might be familiar to you because RNA molecules themselves form hairpin loops, sometimes when they bind to themselves, where they have regions neighboring regions that are complementary, um but not the shape of the structure of our RNA polymerase in pro carry outs. So again the um the RNA or RNA polymerase in pro carry outs and bacteria forms a choice D crab claw structure with the internal channel. See you in the next video.