Concept explainers
A species of bacteria can synthesize the amino acid histidine, so they do not require histidine in their growth medium. A key enzyme, which we will call histidinesynthetase, is necessary for histidine biosynthesis. When these bacteria are given histidine in their growth medium, they stop synthesizing histidineintracellularly. Based on this observation alone, propose three different regulatory mechanisms to explain why histidine biosynthesis ceases when histidine is in the growth medium. To explore this phenomenon further, you measure the amount of intracellular histidinesynthetase protein when cells are grown in the presence and absence of histidine. In both conditions, the amount of this protein is identical. Which mechanism of regulation is consistent with this observation?
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Genetics: Analysis and Principles
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- I have this strain of e coli. Is P+ o+ Z+ Y+ / I- P+ oC Z- Y+ Will beta-galactosidase and permease be expressed? If they are will they be inducible or constitutive?arrow_forwardCTP synthetase catalyzes the glutamine-dependent conversion of UTP to CTP. The enzyme is allosterically inhibited by the product, CTP. Mamma- lian cells defective in this allosteric inhibition are found to have a complex phenotype: They require thymidine in the growth medium, they have unbal- anced nucleotide pools, and they have an elevated spontaneous mutation rate. Explain the likely basis for these observations.arrow_forwardOne single polypeptide chain (120 amino acid residues) is produced for protein A in prokaryotic cell. N-terminal amino acid is alanine in the chain of this protein. How many moles of ATP and GTP will be in use for this polypeptide chain synthesis? What post-translational modifications may be for this protein?arrow_forward
- Describe how one might determine which protein in E. coli are repressed when a culture is shifted from a minimal medium (containing only a single carbon source) to a rich medium containing many amino acids, bases, and vitamins. How might one study which genes are expressed during each growth condition?arrow_forwardConsider the mechanism of the enzyme RNase: What would happen to the Km (i.e., would it increase, decrease, or stay the same) if the his12 was mutated to a lysine? Explain. What would happen to the Kcat (i.e., would it increase, decrease, or stay the same) if the his12 was mutated to a valine? Explain.arrow_forwardDescribe how one might determine which proteins in E.coli are repressed when a culture is shifted from a minimal medium to a rich medium containing many amino acids, bases and vitamins. How might one study which genes are expressed during each growth condition?arrow_forward
- Many blood clotting proteins undergo a post-translational modification in which specific glutamic acid residues (Glu) in the protein are converted to gamma-carboxyglutamic acid residues (Gla). See reaction scheme below. An example is the blood clotting protein Factor IX, which has 12 Glu in its N-terminus converted to Gla. This modification gives Factor IX the ability to bind calcium and phospholipid membranes. Bacteria do not have the enzyme required to convert Glu to Gla and therefore Factor IX proteins expressed in bacteria would not have the proper modifications. How might you engineer the translational apparatus of a bacterial cell line so that it produces Factor IX with Gla in the appropriate positions. How would you ensure that only the 12 Glu in Factor IX that are normally converted to Gla and not just all Glu (Limit 5-6 senetnces)?arrow_forwardwhat is the nature and likely location(s) of a mutant that would, 1)allow constitutive expression of the lac gene? 2)prevent the cell from responding to lactose ( genes are not induced when exposed to lactose)? 3) not allow the cell to utilize lactose even when the genes are inducedarrow_forwardDescribe results that could be obtained from ribosomeprofiling that would indicate the existence of aregulatory mechanism operating at the level oftranslational initiation.arrow_forward
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