1. You are studying an E. coli gene that specifies a protein. A part of its sequence is -Ala-Pro-Trp-Ser-Glu-Lys-Cys-His You recover two mutants for this gene that show no enzymatic activity. By isolating the mutant enzyme products, you find the following sequences: Mutant 1: Ala-Pro-Trp-Arg-Glu-Lys-Cys-His Mutant 2: Ala-Pro- What is the molecular basis for mutation 1 and for mutation 2? What is the DNA sequence that specifies this part of the protein? Wild-type amino acid sequence: NH3-Ala-Pro-Trp-Ser-Glu-Lys-Cys-His-COOH Mutant 1: NH3-Ala-Pro-Trp-Arg-Glu-Lys-Cys-His-COOH Mutant 2: NH3-Ala-Pro-

1. You are studying an E. coli gene that specifies a protein. A part of its sequence is -Ala-Pro-Trp-Ser-Glu-Lys-Cys-His You recover two mutants for this gene that show no enzymatic activity. By isolating the mutant enzyme products, you find the following sequences: Mutant 1: Ala-Pro-Trp-Arg-Glu-Lys-Cys-His Mutant 2: Ala-Pro- What is the molecular basis for mutation 1 and for mutation 2? What is the DNA sequence that specifies this part of the protein? Wild-type amino acid sequence: NH3-Ala-Pro-Trp-Ser-Glu-Lys-Cys-His-COOH Mutant 1: NH3-Ala-Pro-Trp-Arg-Glu-Lys-Cys-His-COOH Mutant 2: NH3-Ala-Pro-

Name: 1. You are studying an E. coli gene that specifies a protein. A part o
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Description: 1. You are studying an E. coli gene that specifies a protein. A part of its sequence is -Ala-Pro-Trp-Ser-Glu-Lys-Cys-HisYou recover two mutants for this gene that show no enzymatic activity. By isolating the mutant enzyme products, you find the follo

Human Heredity: Principles and Issues (MindTap Course List)

11th Edition

ISBN:9781305251052

Author:Michael Cummings

Publisher:Michael Cummings

Chapter9: Gene Expression And Gene Regulation

Section: Chapter Questions

Problem 18QP: The following is a portion of a protein: met-trp-tyr-arg-gly-pro-thr-Various mutant forms of this...

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You are studying an E. coli gene that specifies a protein. A part of its sequence is–Ala–Pro–Trp–Ser–Glu–Lys–Cys–His–You recover a series of mutants for this gene that show no enzymatic activity. By isolating the mutant enzyme products, you find the following sequences:Mutant 1:–Ala–Pro–Trp–Arg–Glu–Lys–Cys–His–Mutant 2:–Ala–Pro–Mutant 3:–Ala–Pro–Gly–Val–Lys–Asn–Cys–His–Mutant 4:–Ala–Pro–Trp–Phe–Phe–Thr–Cys–His–What is the molecular basis for each mutation? What is the DNA sequence that specifies this part of the protein?
Several genes code for enzymes that are responsible for histidine biosynthesis in Escherichia coli. Part of the nucleotide sequence of the gene that codes for one of these enzymes is: AUG CCU UGG GCC CAA AAA UGC A series of mutants that have lost activity for this enzyme are recovered. The mutant products are analyzed and found to have the following amino acid sequences: Mutant 1: Met-Pro-Trp-Pro-Glu-Lys-Cys Mutant 2: Met-Pro Mutant 3: Met-Pro-Cys-Gly-Pro-Lys-Met Mutant 4: Met-Pro-Trp-Pro-Lys-Asp Choose the correct type of mutation that occurred in the DNA to produce each mutant type. Nonsense Answer Missense Answer Addition Answer Deletion Answer
Consider the peptide Asp-Lys-Phe-Glu-Asn-Tyr-Gln-Val-Cys. In a single beaker, you treat this peptide with 2 proteases. One protease cleaves at the N-terminus of aromatic R groups and the other cleaves at the C-terminus of polar, non-ionizable R groups. Following the enzymatic digestion, you want to separate your peptide fragments so that you can identify them. You choose to separate the fragments using an anion exchange column. Beginning at pH=6 you apply your peptide fragments to the column and you gradually decrease the pH of the column stopping the separation when the pH of the column equals 4. Omitting chemical structures, write the amino acid sequence of the peptide fragments that are produced from this digest. Write the order that these fragments will elute from the column (if at all). (Relevant pKa values are: 2.1, 3.8, 4.3, 8.3, 9.6, 10.1, and 10.5)
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)?
You isolate an E. coli strain in which a mutation in the gene encoding the tRNAAla synthetase enzyme causes it to charge both tRNAAla and tRNACyS TRNAS with Alanine (Ala). You sequence the N-terminus of a protein, which normally has the sequence: Met-Cys-Ala-Thr-Tyr-- Which sequence(s) do you expect to obtain? Select one: O Met-Cys-Ala-Thr-Tyr---- O Met-Cys-Cys-Thr-Tyr---- O Met-Ala-Ala-Thr-Tyr---- O Met-Cys-Ala-Thr-Tyr---- + Met-Cys-Cys-Thr-Tyr---- O Met-Cys-Ala-Thr-Tyr---- + Met-Ala-Ala-Thr-Tyr----
Consider the hypothetical serine protease, which shows the specificity pockets. The S, pocket has a glutamic acid in the bottom, the S, pocket is small and hydrophobic, and the S,' pocket is deep and hydrophobic. Suggest an amino acid sequence that this protease would cleave. HRY S2 Si Which of the sequences would this protease cleave? O Lys-Ala-Leu O Ala-Lys-Leu Leu-Ala-Lys Ala-Leu-Lys O Leu-Lys-Ala O Lys-Leu-Ala C=O
A protein substrate is known to be multi-monoubiquitinated. The control lane "C" in the SDS-PAGE gel shows a properly ubiquitinated protein substrate. Please draw out what the lane would look like if all lysine residues except for one are mutated to alanine residues in the protein substrate. Use one sentence to explain your rationale. C 1 Protein Substrate ||||
Wild-type E. coli cells can synthesize all 20 common amino acids, but some mutants, called amino acid auxotrophs, are unable to synthesize a specific amino acid and require its addition to the culture medium for optimal growth. Besides their role in protein synthesis, some amino acids are also precursors for other nitrogenous cell products. Consider the three amino acid auxotrophs that are unable to synthesize glycine, glutamine, and aspartate, respectively. Match each nitrogenous product with the mutant or mutants that would fail to synthesize it. Each mutant may fail to synthesize more than one nitrogenous product, and some nitrogenous products may fail to be synthesized by more than one mutant. glycine auxotrophs glutamine auxotrophs aspartate auxotrophs Answer Bank adenine nucleotides cytosine nucleotides guanine nucleotides uridine nucleotides
Identify the following mutations and describe what the possible effect on the protein will be. (4) 5’GAT TTT AGC TTA GCC CAT 3’ 5’ GAT TAG CTT AGC CCA T 3’ 3’CTA AAA TCG AAT CGG GTA 5’ 3’ CTA ATC GAA TCG GGT A 5’ 5’ GAT TTT AGC TTA CCC CAT 3’ 5’ GAT TTT AGC TAA CCC CAT 3’ 3’ CTA AAA TCG AAT GGG GTA 5’ 3’ CTA AAA TCG ATT GGG GTA 5’
2) A group of three researchers (who often tend to disagree with one another) isolated a new protein and found that the gene sequence of this protein contained a Cys-X3-Cys-X2-Cys-X2-Cys motif (where X is any amino acid). а) you agree? Briefly explain why (or why not). One of the researchers suggested that this must be an enzyme containing a Mn-cluster. Do b) center and this Zn site must have a structural (rather than catalytic) role. Do you agree (or disagree) that this would indeed be a structural Zn site? Briefly explain. The second researcher instead claimed that this must be a protein containing a single Zn
1. The following synthetic polynucleotide is synthesized and used as a template for peptide synthesis in a cell-free system from E. coli. ..AUAUAUAUAUAUAU-… What polypeptide would you expect to be produced? Precisely what information would this give you about the code? 2. If the same polynucleotide described in Problem 1 is used with a mitochondria-derived cell-free protein-synthesizing system, the product is .Met-Tyr-Met-Tyr-Met-Tyr-.. What does this say about differences between the mitochondrial and bacterial codes?
The objective is to study a novel protease P isolated from the digestive tract of an Amazonian insect. This protease can exist into two forms Pi and Pa which have identical amino acid sequences (both of 80 kDa). However, only Pa shows proteolytic activity. To better understand the activation mode of Pi (inactive form) in Pa (active form), the following experiment was done using DIPF. DIPF (diisopropylphosphofluoridate) is a well-known irreversible inhibitor of serine proteases. It reacts with the catalytic serine residue of the active site of proteases as shown below: Enzyme -CH₂OH + CH(CH3)2 O F-P=0 O CH(CH3)2 Diisopropylphospho- fluoridate (DIPF) Enzyme -CH,—O CH(CH3)2 O <=0 O CH(CH3)2 DIP-Enzyme Both proteases Pa and P₁ were incubated with 32P-DIPF for 30 min at 37°C, and then dialysed to remove excess of unreacted radiolabelled reagent. The two proteases were then analyzed in Sodium Dodecyl Sulphate-Polyacrylamide Gel Electrophoresis (SDS-PAGE), with and without 2-mercaptoethanol.…