Biochemistry: Concepts and Connections (2nd Edition)
2nd Edition
ISBN: 9780134641621
Author: Dean R. Appling, Spencer J. Anthony-Cahill, Christopher K. Mathews
Publisher: PEARSON
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Chapter 6, Problem 21P
In most cases, mutations in the core of protein that replace a smaller nonpolar side chain in the wild-type (e.g., Ala, Val) with a larger nonpolar side chain (e.g., Leu, lle, Phe, Trp) in the mutant, result in significant destabilization and misfolding of the mutant. What feature of the protein core explains this observation? Why would such a mutation prevent a protein from folding properly?
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Chapter 6 Solutions
Biochemistry: Concepts and Connections (2nd Edition)
Ch. 6 - Prob. 1PCh. 6 - Bovine pancreatic trypsin inhibitor (BPTI; Figure...Ch. 6 - A schematic structure of the subunit of...Ch. 6 - In the protein adenylate kinase, the C-terminal...Ch. 6 - Give two reasons to explain why a proline residue...Ch. 6 - Consider a small protein containing 101 amino acid...Ch. 6 - a. Based on a more conservative answer to Problem...Ch. 6 - The following sequence is part of a globular...Ch. 6 - a. A protein is found to be a tetramer of...Ch. 6 - Under physiological conditions, the protein...
Ch. 6 - Theoretical and experimental measurements show...Ch. 6 - The peptide hormone vasopressin is used in the...Ch. 6 - A protein gives under conditions of buffer...Ch. 6 - A protein gives a single band on SDS get...Ch. 6 - It has been postulated that the normal...Ch. 6 - Below are shown two views of the backbone...Ch. 6 - Do you expect a Pro Gly mutation in a...Ch. 6 - Rank the following in terms of predicted rates...Ch. 6 - Shown below are two cartoon views of the small...Ch. 6 - Prob. 20PCh. 6 - In most cases, mutations in the core of protein...Ch. 6 - A Leu Ala mutation at a site buried the core of...Ch. 6 - Disulfide bonds have been shown to stabilize...Ch. 6 - Cartoon renderings of the proteins Top 7 and adaH2...
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- The following is a portion of a protein: met-trp-tyr-arg-gly-pro-thr-Various mutant forms of this protein have been recovered. Using the normal and mutant sequences, determine the DNA and mRNA sequences that code for this portion of the protein, and explain each of the mutations. a. met-trp- b. met-cys-ile-val-val-leu-gln- c. met-trp-tyr-arg-ser-pro-thr- d. met-trp-tyr-arg-gly-ala-val-ile-ser-pro-thr-arrow_forwardConsider 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)arrow_forwardTo better understand the effects of palmitoylation on protein X, researchers want to chemically attach a palmitic acid at a specific position in this protein. The researchers first try to feed cells with palmitic acid or an amino acid with a C16 side chain. Neither of the initial experiments is successful in helping the researchers learn more about the biological role of palmitoylated protein X. Why? Suggest a strategy to specifically incorporate a palmitoylation site into protein X.arrow_forward
- Q) a) A protein gains a mutation of a surface exposed residue. The mutation is Arg --> Leu. Based on the sequence of the protein when it folds the Leu remains on the surface of the protein. What is the change in chemical characteristic of the amino acid caused by this mutation? b) Briefly explain any entropic consequences of this mutation. (2 sentences MAX) c) What might happen in order to overcome these entropic consequences and how would that affect the cell? (1-2 sentences)arrow_forwardThis problem concerns a "typical" tyrosine residue found on the surface of a globular protein. a) If the pKa of this residue is 10.1, at what pH will this residue be found in its deprotonated state in 99% of protein molecules? b) How would the presence of a neighboring negatively charged residue effect the equilibrium expression for the dissociation of tyrosine? c) Would the presence of the negatively charged residue raise or lower the pKa of this tyrosine? Justify and/or explain your answers in 1–2 sentences each for parts b) and c).arrow_forwardConsider a short peptide that forms an alpha-helix within a larger protein structure. Suppose that one glutamate residue at some specific position in the helix were mutated to a leucine residue. The mutation could either make the helix more stable, or less stable. i) Describe two situations in which a Glu-to-Leu mutation could make the helix more stable. ii) Describe two situations in which the Glu-to-Leu mutation could make the helix less stable. Explain briefly the basis for the stabilizing and destabilizing effect in all cases.arrow_forward
- This problem concerns a "typical" tyrosine residue found on the surface of a globular protein. a) If the pk3 of this residue is 10.1, at what pH will this residue be found in its deprotonated state in 99% of protein molecules? b) How would the presence of a neighboring negatively charged residue effect the equilibrium expression for the dissociation of tyrosine? c) Would the presence of the negatively charged residue raise or lower the pK3 of this tyrosine? Justify and/or explain your answers in 1-2 sentences each for parts b) and c).arrow_forwardPeptides and small proteins fold spontaneously in aqueous solution at room temperature. Thus, for a small protein in water, we can say ΔG FOLD < 0. Denoting the unfolded protein as Unf and the folded protein as Fld, we can write the following equation:Unf(aq)--DELTA G FOLD----> Fld(aq)Considering the transition from the unfolded state (in which there are many possible conformations) to the folded state (only one conformation), there is clearly a decrease in the entropy of the protein. However, protein folding is (correctly) described as an entropically driven process.a) Resolve this apparent paradox by identifying the enthalpy (ΔH) and entropy (−TΔS)components involved in protein…arrow_forwardThe figure shows an example of a thermal denaturation plot. The melting temperature (Tm) is the midpoint of the temperature range over which denaturation occurs. Percent unfolded 100 80 60 40 20 0 20 Tm 40 60 Temperature (°C) 80 100arrow_forward
- In the fungus Neurospora, some mutants were obtained that lacked activity for a certain enzyme. The mutations were found, by mapping, to be in either of two unlinked genes. Provide a possible explanation in reference to quaternary protein structure.arrow_forwardAssume that the 3 polypeptide strands shown below form a parallel B-sheet. Select amino acids AA1, AA2, and AA3 so that the parallel B-sheet is amphipathic and remains stable. Glu-lle-Asn-AA1-Cys-Val Ser-AA2-GIn-Leu-Lys-Phe Lys-Met-Cys-Leu-AA3-Val O AA1 = Pro, AA2 = Leu, AA3 = lle O AA1 = Val, AA2 = Leu, AA3 = Asn O AA1 = Ala, AA2 = Gly, AA3 = Leu AA1 = Phe, AA2 = Arg, AA3 = Ala O Oarrow_forwardConsider the following in light of the concept of levels of structure (primary, secondary, tertiary, quaternary) as defined for proteins. (a) What level is shown by doublestranded DNA? (b) What level is shown by tRNA? (c) What level is shown by mRNA?arrow_forward
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