Genetic Regulation and the Lactose Operon

ID #1413

I am confused on the slide about how much it costs to make a protein. Am I right if I state that if you have a gene (lacZ) that is 3,000 nucleotides long, it will uses up (3000 ATP) and give you a mRNA , so in this case, you use 3 ATP per amino acid and therefore if you use 3000ATP, you will have a 1000 AA protein. I'm confused at the part from 3000 nucleotides you get 3000 ATP in the slide, because if you had given us just a 3000 nucleotide gene, then how do I know it uses 3000ATP to make a protein?

If I'm interpreting your question correctly, it looks like you're not taking into account that it "costs" energy to do both transcription AND translation. Using that example, your cost for transcription is one ATP equivalent (ATP, UTP, GTP, or CTP) per base added into the mRNA. 3000 bases in the template strand = 3000 ATP equivalents for transcription. If your coding region in your mRNA has 3000 bases in it, it will be translated into a 1000 amino acid protein. The cost for translation is 3 ATP equivalents (ATP or GTP) per amino acid, or 1000 x 3 = 3000 more ATP equivalents. That brings the grand total up to 6000 ATP equivalents per molecule of this protein for full expression.

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