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 23P
Disulfide bonds have been shown to stabilize proteins (i.e., make them less likely to unfold). Consider the cases shown schematically below for two variants of the same protein. In case #1 the disulfide forms between Cys residues that have been introduced near the protein N- and C-termini, and in case #2 the disulfide forms between Cys residues that have been introduced in the middle of the protein sequence. Which protein is likely to be more stable? (Note: Assume the disulfide bond is intact in both the unfolded and folded states). Explain your reasoning.
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You have discovered a novel protein that has a pI = 5.5. To study the functional properties of this new protein, your research group has made a mutant that contains two amino acid changes—namely, a surface Phe residue in the normal protein has been replaced by His (side chain pKa = 6.1) and asurface Gln has been replaced by Glu (side chain pKa = 6.0). Is the pI of themutant protein predicted to be greater than, less than, or the same as the pIof the normal protein? Support your answer with the appropriate calculation
You have discovered a novel protein that has a pl = 5.5. To study the
functional properties of this new protein, your research group has
made a mutant that contains two amino acid changes: a surface
phenylalanine residue in the normal protein has been replaced by
histidine (side chain pK, = 6.1), and a surface glutamine has been
replaced by glutamic acid (side chain pK, = 6.0). Is the pl of the
mutant protein predicted to be greater than, less than, or the same as
the pI of normal protein? Support your answer with the appropriate
calculation.
1) You are studying the toxic protein called ectatomin, a major component of ant venom
(specifically from the species Ectatomma tuberculatum), that embeds into cell
membranes and creates pores that cause cells to lyse. Ectatomin is a small dimer,
meaning the protein is comprised of two polypeptides; the sequences of the two
polypeptides are given in the table with single-letter abbreviations.
polypeptide sequences of ectatomin monomers
polypeptide
|protein sequence
polypeptide 1
GVIPKKIWETVCPTVEPWAKKCSGDIATYIKRECGKL
polypeptide 2
WSTIVKLTICPTLKSMAKKCEGSIATMIKKKCDK
You could use absorbance at 280nm or colorimetric assays like the Bradford assay or
bicinchoninic acid assay (BCA) assay to quantify the amount of ectatomin you have for
your experiment.
Why might you choose to use a colorimetric method instead of absorbance at 280nm?
Select the best answer.
a) Measuring absorbance at higher wavelengths, like 595nm or 562nm, is more accurate
than measuring absorbance at 280nm.
b) The Bradford…
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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Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, biochemistry and related others by exploring similar questions and additional content below.Similar questions
- You have discovered a novel protein that has a pl = 5.5. To study the functional properties of this new protein your research group has made a mutant that contains two amino acid changes-namely, a surface Phe residue in the normal protein has been replace by His (side chain pk = 6.1), and a surface Gln has been replace by Glu (side chain pk. = 6.0). The pl of the mutant protein is predicted to be: A. Greater than the pl of the normal protein. B. Less than the pl of the normal protein. C. The same as the pl of the normal protein.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_forwardImagine a globular protein with a histidine that is involved in a salt bridge to an aspartic acid, in an internal (hydrophobic) region of the protein. What would happen to the pKa of that histidine R group if the protein was mutated, and the aspartic acid was replaced with an alanine? (i.e., would the pKa increase, decrease, or stay the same?). Assume that the location of the histidine stays the same. Explain your answer clearlyarrow_forward
- Suppose that there is an unknown protein that underwent Edman sequencing method. From N- terminal determination, a biochemist found out that there are two N-terminal amino acid residues, V and G. What is the original sequence of the protein given the following peptide fragments: after digestion with Chymotrypsin: G-L-S-R-G-M-w V-A-L-F Q-L-Y L-R-V-W G-M-V-E-A-D-I-P K-S-P-E-M-T-W R-M-A-S-E-K-P-G-H after digestion with Trypsin: P-G-H V-W-G-M-V-E-A-D-I-P M-A-S-E-K G-M-W-Q-L-Y-L-R S-P-E-M-T-W-R G-L-S-R V-A-L-F-K after digestion with Cyanogen Bromide: T-W-R-M W-Q-L-Y-L-R-V-W-G-M V-E-A-D-I-P A-S-E-K-P-G-H V-A-L-F-K-S-P-E-M G-L-S-R-G-Marrow_forwardis it true that aplha and beta are made up of same amino acids but Beta chain is longer than alpha chain？what is other difference and similarity？is the amino aicd sequence exactly the same as well？are their structure the same ？arrow_forwardIn the molecule of oligomeric protein there are 19 lysine residues. 12 of them may be easily acetylated with anhydrides of dicarbon acids (it react with NH2-groups). The acetylation of extra two residues of lysine will dissociate the protein to the subunits. The rest 5 lysine residues may be modified only after denaturation of the protein. Suggest, how many lysine residues are: a) on a surface of protein globule; b) inside globule: c) in a site which is responsible for the contact within subunitsarrow_forward
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- A recent genome sequencing project for the bacterium Burkholderia mallei has identified a new protein with high similarity to the lysylphosphatidylglycerol flippase enzyme. A short section of the new protein sequence is shown below. TVEVNAPGDVQKALSELQQINDGRLDIRI (a) Are any reverse turns likely to be present? Explain your answer. (b) Are any beta-strands likely to be present? Explain your answer. (c) Are any alpha helices likely to be present? Explain your answer. (d) Is any supersecondary structure likely to be present? Explain your answer. (e) Identify two residues that are likely to be buried in the core of the folded protein. Explain your answer. (f) Identify two residues that are likely to be hydrogen bonded to each other. Explain your answer.arrow_forwardThe OXA-M290 protein is next purified by size exclusion chromatography. To determine the best type of size exclusion resin to use, the size of OXA-M290 must first be determined. Earlier, you determined the amino acid sequence of OXA-M290 (MRVLALSAVFLVASIIGMPAVAKEWQENKSWNAHFTEHKSQGVVVLWNENKQQGFTNNLKRANQAFLPASSAKIPNSLIALDLGVVKDEHQVFKWDGQTRDIATWNRDHNLITAMKYSVVPVYQEFARQIGEARMSKMLHAFDYGNEDISGNVDSFWLDGGIRISATEQISFLRKLYHNKLHVSERSQRIVKQAMLTEANGDYIIRAKTGYDTKIGWWVGWVELDDNVWFFAMNMDMPTSDGLGLRQAITKEVLKQEKIIP). Based on the amino acid sequence, what is the molecular weight of this protein? You can use the free ProtParam tool (https://web.expasy.org/protparam/) to calculate the molecular weights of proteins. Make sure to include units in your answer. Note: The amino acid sequence reported earlier does not include the His-tag that was added to OXA-M290 by the pET-28a vector. However, you do not need to consider the amino acids in the His-tag in your answer to this question. For Context ONLY: For…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_forward
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