7.What is an allosteric effect? What is are homotropic and heterotropic allostery? Name one exampleof homotropic allostery.8.The graph below describes the binding curve of three difference proteins to the same ligand (L).(a) Define what ¤, [L] and Kå signify on this graph.(b) Which protein has the highest affinity for the ligand?(c) Do these proteins bind the ligand cooperatively? Why or why not?(d) For the binding reaction described in the green curve, at which concentration of L would 50% ofthe binding sites be occupied? Why?Ꮎ0.5K=1 nMK=10 nM0.0+ŏ K₁K=100 nM20406080[L] (nM)

Q. 8. ANSWER. (a) θ (Theta): This represents the fraction of protein molecules that bind to the…

Answered: 7.What is an allosteric effect? What is…

Biochemistry

9th Edition

ISBN:9781319114671

Author:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.

Publisher:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.

Chapter1: Biochemistry: An Evolving Science

Section: Chapter Questions

Problem 1P

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What effect does a negative effector have on the graph of reac- tion rate (V) vs. [substrate] for an allosteric effector?
For the protein Calmodulin-1: 1) this protein have any secondary, tertiary and/or quaternary structures present? 2) Are there any molecular additions to this protein that are not amino acids?For both questions, can you explain if so, where specifically? The protein Calmodulin-1 is stated to have the molecular function of signaling receptor binding which is interrelated with the biological function of calcium-mediated signaling. Can you explain this relationship?
2. The following tyrosine-phosphorylated polypeptides were tested as substrates of protein tyrosine phosphatase, an important enzyme in cellular signal transduction. The pTyr in bold signifies the tyrosine residue that is phosphorylated. The binding affinities of the polypeptide substrates to the enzyme were found to follow the order: (a) > (c) - (d) >> (b). (a) Asp-Ala-Asp-Glu-pTyr-Leu-lle-Pro-Gln-Gln-Gly (b) Pro-Val-Pro-Glu-pTyr-lle-Asn-Ala-Ser-Val (c) Asp-Ala-Glu-Glu-pTyr-Leu-Val-Pro-Gln-Gln-Gly (d) Asp-Asn-Leu-Tyr-pTyr-Trp-Asp-Glu-Asn-Ser-Ser In addition to the presence of the phosphorylated tyrosine residue, what amino acid a) properties of the polypeptides accounts for the relative order of binding affinities to the enzyme? b) the active site of the phosphatase enzyme that are responsible for the affinity of substrate binding? Assume a pH of 7.4 at the enzyme active site. (Note a phosphatase uses phosphate substrate) What amino acids have side chains that would indicate they are…
You have purified Protein 'X' and you want to know its concentration. As we learned, you can calculate concentrations by simply measuring UV280 absorbance of protein solutions. Using a UV spectrophotometer, you measured an absorbance of 0.6. Given that Protein X has an absorptivity (or extinction coefficient) of 0.2 mL•mg-cm at 280 nm, what is the concentration of purified protein solution (assume the light path is 1 cm)? -1 O A. 3 g/mL B. 3 mg/mL OC.0.2mg/mL OD.0.2 g/mL OE. 0.6 g/mL
For a binding protein to show positive cooperativity…. Choice 1 of 4:the protein must be able to adopt at least 2 different conformations each with different affinities for the ligand Choice 2 of 4:the protein must be able to bind to at least 2 different types of ligand Choice 3 of 4:the protein must bind to one molecule of ligand fast and one molecule of ligand slowly Choice 4 of 4:the Kd must be in the micromolar range
You are studying how your Lys-Val-Thr tripep de interacts with another pep de, which places an Asp in close proximity to the Lys on your pep de. How would the presence of an Asp side chain affect the pKa of the Lys side chain? Briefly explain your reasoning. (remember pKas are rela ve, pKa=log([H+][A-]/[HA])
A one-to-one protein (P)-ligand (L) complexation (P + L PL) has a dissociation equilibrium constant (Kd) value of 100 nM at 25°C, and the Kd remains the same at 37°C. 1) What is AS of binding at 25°C? Assume ACp of the binding is 0 over the temperature range. AS = 1.34E2 kJ/(mol*K) (note the unit!!) (sig. fig =3) 2) What is the concentration of the PL complex formed at equilibrium when you mix 0.20 uM (microM) of Protein and 1.0 uM of Ligand together at 37°C? PL at equilibrium = 8.1E-1 uM (note the unit!!) (sig. fig =2)
Two proteins, A and B, bind to the same ligand, L, with the binding curvesshown below. What is the dissociation constant, Kd , for each protein? Which protein (A or B) has a greater affinity for ligand L?
The amide hydrogen atoms of peptide bonds within proteins can exchange with protons in a solvent. In general, amide hydrogen atoms in buried regions of proteins and protein complexes exchange more slowly than those on the solvent-accessible surface. By determining these exchange rates, we can explore protein-folding reactions, probe the tertiary structure of proteins, and identify the regions of protein-protein interfaces. We can investigate these exchange reactions by studying the behavior of the protein in solvent that has been labeled with deuterium, 2H, a stable isotope of hydrogen. Select the methods that could be readily applied to the study of hydrogen-deuterium exchange rates in proteins. enzyme-linked immunosorbent assay (ELISA) nuclear magnetic resonance (NMR) spectroscopy x-ray crystallography mass spectrometry (MS)
An engineered ligand binds its target with 5 nM affinity at high pH. However, protonation of a histidine residue in the binding site of the ligand renders it unable to bind. Plot the ligand:target complex concentration versus the initial ligand concentration (in protonated or unprotonated form) at pH 4, 5, 6, 7, or 8 (five lines on one plot). Use a total target concentration of 10 nM.
Small molecules are used as inhibitors of protein action - as drugs. They most often do this by blocking the active site within the protein. Potential drugs can be screened computationally to determine if they are strongly bound to the protein. Figure 1 shows a possible conformation of a candidate drug molecule, 4-bromo-2- carboxymethylamide-pyrrole (abbreviation: BCMAP) at the active site of a protein (abbreviation: PR). Figure 2 shows the full protein structure whilst figure 3 shows a known inhibitor of the protein at the site, overlayed with another calculated conformer of BCMAP. (a) Explain what types of interactions, both intermolecular and intramolecular, that a molecular mechanics forcefield must be able to describe in order to be able to accurately determine the geometry of BCMAP in the protein. Identify which interactions will be the most important to describe accurately. Figure 1.4-bromo-2-carboxymethylamide-pyrrole (BCMAP) (C, N, O, and Br atoms in yellow, blue, red, and…
What amino acids can be found in chymotrypsin’s specificity pocket? What would happen if one of those amino acids was changed to lysine? In relation to the amino acid in the specificity pocket, which peptide bond is cleaved; C terminal or N terminal? What is this bond’s proximity to the serine in the active site?

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