BACKGROUND: The sequencing of a newly discovered, unusual microorganism, Obscura
ID: 83482 • Letter: B
Question
BACKGROUND: The sequencing of a newly discovered, unusual microorganism, Obscura marylandium, reveals that it contains no membrane-bound nutrient receptors/transporters, which are commonly found in organisms ranging from bacteria, plants, and insects to mammals. Instead, it appears that metabolites needed by Obscura marylandium freely diffuse into (and out of) cells through unregulated pores. However, there are a number of small-molecule recognition proteins within the microorganism that bind tightly to metabolites. For example, research in your advisor's laboratory suggests that families of allosteric repressors sense intracellular nutrients and control the transcription of biosynthetic operons according to their quality and availability. Generally, it appears that the repressors can sense both precursors and end products of metabolic pathways. When end products are high in concentration, they stabilize monomeric forms of the repressor, which are able to bind DNA and inhibit transcription of biosynthetic operons. Alternatively, when precursors bind to the repressors, a shift to dimeric structures is promoted. Dimeric repressors are unable to bind DNA, and hence, transcription of biosynthetic enzymes is activated. Also, the lab has shown that there is an additional level of regulation: transcriptionally active repressor monomers bind to and activate a key enzyme that can covalently modify biosynthetic enzymes to increase their activity. Witht this background, please address the following questions:
1a) Without modifying the operator sites of biosynthetic operons, describe a synthetic biology design (or modification of the regulatory circuit described above) that would enable production of end products regardless of metabolite levels, effectively uncoupling metabolite levels from metabolite synthesis (assume any growth media is not nutrient limited). How would you test your design?
Explanation / Answer
In any Operon , that is repressible, the Switch is ON usually. This means the metabolites are produced continously until a repressor comes and binds to the operator. The repressor protein is eynthesized far away from the operator site usually. The repressor protein comes from the regulatory gene.At time of need that is, when product increases the expected level ,the repressor binds to the product, causing inhibition. If the regulatory gene is modified , the repressors are not produced. This causes the metabolite products to be produced continously, without any inhibition. Even small molecules that are called as co-repressors have to bind to repressors, to inhibit operon. So if Repressor is inactive or not produced, the metabolic products do not themselves act as inducers.
To test this in a laboratory, the bacteria can be grown on media containing the substrate in higher levels, to check if the enzyme is inhibited or not. If the enzymes is not inhibited then the substrate is continously used up to produce end product.This can be determined by colorimetric method , to see the rate of absorbance that is directly proportional to product concentration.
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.