Okay, so now let's talk about the trap regulation of the Trabophoran. Prokaryotic cells have been around for a really long time, right? They just are always around. They've been around for so long. And that means that they've had a long time to evolve different ways to do the same thing. And so, occasionally, although we've talked about the main ways the tropoparone is regulated, through the repressor and the attenuation. But occasionally, a few organisms have evolved an additional or separate way of regulating the same operon. So the one that I want to talk to you about was done by this organism here, and it uses a special protein called the trpRNA binding attenuation protein. What happens is that this protein binds to tryptophan. And that means when tryptophan is high, this trap protein is bound to a lot of tryptophan, meaning we call that saturated, right? It's bound to a ton of them. And this trap protein will then bind to the leader sequence that we talked about before. When it binds to the leader sequence, that forms the terminator configuration and stops transcription. Now, what happens when tryptophan is low? So when tryptophan is low, another protein comes in called the anti-trap and that binds to trap instead. And so when anti-trap binds to trap, this allows for the formation of the anti-terminator configuration and that promotes transcription. So the trap-anti-trap regulatory method can actually be sensitive to a wide variety of tryptophan concentrations, because you're dealing with saturation. So trap binds to multiple tryptophans. So there can be intermediate phenotypes for when trap is bound everywhere it can be, it's saturated versus when it's bound to half of the tryptophan molecules, so that binding isn't as strong. So what this looks like, it's a view of high levels of tryptophan. You have TRAP, this gray protein here binding with tryptophan, these red dots, and this forms the and or the terminator sequence and that stops transcription. And then when tryptophan concentration is low, you have trap and anti-trap bound. This forms the anti-terminator and that allows for transcription to continue. So this is just one of many ways actually that prokaryotic cells have independently evolved how to regulate the tryptophan operon. Now the repressor and the attenuation are definitely the top two main ways that prokaryotics do this. But I wanted to mention this because, first, it's mentioned in your book and you may need to know it, but second, because it really highlights the way that prokaryotic cells don't necessarily all regulate the same gene the same way. And so, many of them, because they've been around for so long, have evolved sort of independent, but similar ways to regulate the same operon. So I've been telling you about the main ways and those are the most important. Right? Those are the big examples to know. But know that there are so many different ways to regulate the same thing in prokaryotic cells. So with that, let's now move
Table of contents
- 1. Introduction to Genetics51m
- 2. Mendel's Laws of Inheritance3h 37m
- 3. Extensions to Mendelian Inheritance2h 41m
- 4. Genetic Mapping and Linkage2h 28m
- 5. Genetics of Bacteria and Viruses1h 21m
- 6. Chromosomal Variation1h 48m
- 7. DNA and Chromosome Structure56m
- 8. DNA Replication1h 10m
- 9. Mitosis and Meiosis1h 34m
- 10. Transcription1h 0m
- 11. Translation58m
- 12. Gene Regulation in Prokaryotes1h 19m
- 13. Gene Regulation in Eukaryotes44m
- 14. Genetic Control of Development44m
- 15. Genomes and Genomics1h 50m
- 16. Transposable Elements47m
- 17. Mutation, Repair, and Recombination1h 6m
- 18. Molecular Genetic Tools19m
- 19. Cancer Genetics29m
- 20. Quantitative Genetics1h 26m
- 21. Population Genetics50m
- 22. Evolutionary Genetics29m
12. Gene Regulation in Prokaryotes
Tryptophan Operon and Attenuation
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Tryptophan Operon and Attenuation practice set
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