Call us toll-free

Quick academic help

Don't let the stress of school get you down! Have your essay written by a professional writer before the deadline arrives.

Calculate the price


275 Words


RNA-Based Regulation | Boundless Microbiology

Repression of the trp operon is sensitive to slight to moderate decreases in intracellular tryptophan concentration. In contrast, attenuation is designed to allow transcription of the structural genes of the operon only when there is nearly complete depletion of the pool of charged tRNATrp. This occurs under two conditions; when the supply of intracellular tryptophan is grossly insufficient and/or when the demand for Trp-tRNATrp greatly exceeds its availability. As we shall describe, the leader peptide coding region, trpL, of the trp operon of these two bacterial species has only two tryptophan codons, which are adjacent. This design allows relief of termination only when the intracellular concentration of Trp-tRNATrp is so low that rapid translation of both of these tryptophan codons cannot occur.

F’ I+-p+ocZ-Y+ X F- Isp+o+Z+Y+ 2~3 Describe the effects on attenuation and on tryptophan ..

Transcription of the five major structural genes of the trp operon of E. coli and S. enterica is regulated by both repression and transcription attenuation. As previously mentioned, these regulatory mechanisms allow a response, respectively, to changes in the intracellular concentrations of tryptophan and tryptophan-charged tRNATrp, Trp-tRNATrp. The intracellular tryptophan concentration is determined by several events: tryptophan import from the cell’s environment, tryptophan produced internally by biosynthesis, and the rate of use of tryptophan during protein synthesis. The concentration of charged tRNATrp also depends on several factors: the intracellular concentrations of tryptophan, tRNATrp, and tryptophanyl-tRNA synthetase (see Aminoacyl tRNA Synthetases), and the overall rate of protein synthesis. It is apparent that the regulatory strategies that control transcription of the trp operon of E. coli and S. enterica were designed to adjust the rate of synthesis of this amino acid in response to all extracellular and intracellular events that alter the availability of tryptophan and Trp-tRNATrp for protein synthesis. Feedback inhibition of anthranilate synthase provides an additional important level of regulation by tryptophan by controlling entry of chorismate into the biosynthetic pathway.

Attenuation of the Tryptophan Operon: ..

Feedback inhibition of anthranilate synthase can have a significant impact on the extent of repression. Thus, when E. coli is synthesizing the tryptophan it needs for growth and thus, repression is incomplete, feedback inhibition by the available tryptophan partially inhibits anthranilate synthase activity. This results in the production of slightly higher levels of the tryptophan biosynthetic enzymes, which is achieved by partial relief of repression. Feedback inhibition is a particularly effective regulatory mechanism because it reduces tryptophan synthesis instantaneously, whereas repression and attenuation have delayed effects. By employing complementary regulatory mechanisms, E. coli and S. enterica exploit the advantages that can be derived from different means of sensing and responding to tryptophan availability for protein synthesis.

The principal trp promoter, trpP1, is a relatively strong promoter; in tryptophan-deficient cells, RNA polymerase can initiate transcription at this promoter every 4-5 seconds (3). Inasmuch as a transcribing polymerase molecule could reach the attenuator region within a few seconds, it is essential that the decision be made quickly whether or not to terminate transcription at the attenuator. Because this decision is based on the transcript position of the ribosome that is attempting synthesis of the leader peptide, it is essential to synchronize translation of the leader peptide coding region with transcription of the leader region. Synchronization is achieved by features of the nucleotide sequence of the leader transcript; other features of the transcript determine the appropriate transcription termination response, which depends on the cellular level of charged tRNATrp (3).

BIOL 2153 Smith Exam 4 Flashcards | Quizlet

Order now

    As soon as we have completed your work, it will be proofread and given a thorough scan for plagiarism.


    Our clients' personal information is kept confidential, so rest assured that no one will find out about our cooperation.


    We write everything from scratch. You'll be sure to receive a plagiarism-free paper every time you place an order.


    We will complete your paper on time, giving you total peace of mind with every assignment you entrust us with.


    Want something changed in your paper? Request as many revisions as you want until you're completely satisfied with the outcome.

  • 24/7 SUPPORT

    We're always here to help you solve any possible issue. Feel free to give us a call or write a message in chat.

Order now
  • You submit your order instructions

  • We assign an appropriate expert

  • The expert takes care of your task

  • We send it to you upon completion

Order now
  • 37 684

    Delivered orders

  • 763

    Professional writers

  • 311

    Writers online

  • 4.8/5

    Average quality score

Order now
  • Kim

    "I have always been impressed by the quick turnaround and your thoroughness. Easily the most professional essay writing service on the web."

  • Paul

    "Your assistance and the first class service is much appreciated. My essay reads so well and without your help I'm sure I would have been marked down again on grammar and syntax."

  • Ellen

    "Thanks again for your excellent work with my assignments. No doubts you're true experts at what you do and very approachable."

  • Joyce

    "Very professional, cheap and friendly service. Thanks for writing two important essays for me, I wouldn't have written it myself because of the tight deadline."

  • Albert

    "Thanks for your cautious eye, attention to detail and overall superb service. Thanks to you, now I am confident that I can submit my term paper on time."

  • Mary

    "Thank you for the GREAT work you have done. Just wanted to tell that I'm very happy with my essay and will get back with more assignments soon."

Ready to tackle your homework?

Place an order