In one type of hemoglobin variant, lysine EF6 is replaced by an aspartic acid residue.What would be the effects of this mutation on the affinity of the hemoglobin for 2,3BPG and oxygen?The affinity for 2,3-BPG would increase, and for oxygen would decrease.The affinity for 2,3-BPG would decrease, and for oxygen would decrease.The affinities for 2,3-BPG and for oxygen would be unaffected.The affinity for 2,3-BPG would increase, and for oxygen would increase.The affinity for 2,3-BPG would decrease, and for oxygen would increase.

The replacement of lysine (K) by aspartic acid (D) at position EF6 in hemoglobin affects the…

Answered: In one type of hemoglobin variant,…

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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A very new Hemoglobin variant, called Hb simplex, has just been identified in patients with hypoxia (i.e. patients for whom the oxygenation of organs is not properly accomplished). However, this variant is able to bind dioxygen with a Kd which is significantly lower to that of Hemoglobin from normal patients. This effect has been associated with the substitution of a Lys by a Met at two distinct sites of the b subunit of Hemoglobin : one site close to the N-terminus, and the other site close to the C-terminus of the polypeptide chain. Most importantly, these 2 sites are known to be involved in the maintain of the physical interactions between the subunits a and b in Hemoglobin. 1) The aforementioned Hb simplex mutations lead to a loss of physical interactions between the subunits a and b. What type(s) of chemical bonds between the 2 subunits (i.e. covalent, electrostatic, ion-dipole, dipole-dipole, van der waals) would you hypothesize to be affected by these mutations? explain. 2)…
The proximal histidine residues have been replaced by glycine residues by mutation of the cloned genes for both the α and β subunits of hemoglobin. With the tetrameric mutant hemoglobin (all subunits being mutant, α H F8 G, β H F8 G), it was found that the “proximal” coordination bonds to hemes in the mutant protein could be replaced by having the small molecule imidazole in the buffers. Oxygen binding curves for the tetrameric mutant hemoglobin were measured. A. The degree of cooperativity in oxygen binding for the mutant hemoglobin (with imidazole present) would be expected to 1) increase 2) decrease 3) not be affected) compared with the normal protein. B. Justify your answer to part A in terms of what you know about the structural basis of cooperativity in hemoglobin. C. How would the Hill coefficient for the mutant be expected to change compared with nH for normal hemoglobin, which is ~3?
Sickle cell anemia is caused by a point mutation in the β-globin chain of hemoglobin. Glutamic acid is replaced by Valine. HBB sequence in normal adult hemoglobin (Hb A): Leu-Thr-Pro-Glu-Glu-Lys-Ser HBB sequence in mutant adult hemoglobin (Hb S): Leu-Thr-Pro-Val-Glu-Lys-Ser What effect does this mutation have on the structure and function of the protein? Predict what would happen to the RBC if the glutamic acid was replaced with asparagine instead of valine.
Below is a list of hypothetical Hemoglobin variants. Circle the name of the variant that is most likely to show an increase in BPG binding. Does such a hypothetical variant cause an increase or decrease in hemoglobin's affinity for oxygen? A. Hb Miami: Leu is substituted with Pro in an alpha helix B. Hb California: Val is substituted with Lys at pH 7.0 C. Hb New york: Tyr is substituted with Met, which disrupts the hydrogen bonding at the a131 interface. D All of the above
In a molecular disease of hemoglobin, Hemoglobin Rainier, Tyr 145β is replaced by Cys, which forms a disulfide bond with another Cysresidue in the same subunit. This prevents the formation of ion pairs that normally stabilize the T state. How does hemoglobin Rainier differ from normal hemoglobin with respect to the Hill coefficient
When human hemoglobin undergoes a mutation, the mutant protein usually does not replace all of the normal HbA in the red blood cells or erythrocytes of the individual. The erythro- cytes contain mixtures of varying amounts of both HbA and the mutant protein depending on the mutation and the individual. Hb Yakima is a mutant human Hb with an Asp-(B99)His mutation. The diagram on the right shows that Hb Yakima was separated by DEAE-cellulose chromatography from HbA with a 0 – 0.1 M linear gradient of NaCl buffered to pH 8.3. Why is chromatog- raphy carried out at pH 8.3? If the isoelectric point of HbA is 6.85, what is the change in total charge caused by the mutation?How does the change in charge explain the chromatography elution profile of the Hb Yakima/HbA mixture? 1,5 -Hb-A Hb -Yakima 1.0 0.5- 20 40 60 80 00 Fraction number O.D578 nm
The steps involved in the T→ R transition in when oxygen binds to hemoglobin are outlined below. Place them in the correct order (1 = first thing to happen), assuming that it is the oxygen-binding that initiates the transition and that the process occurs in discrete steps. The proximal histidine is pulled by the heme iron. The F helix is pulled out of place, breaking a network of salt bridges. The iron is pulled into the plane of the protoporphyrin IX ring. Oxygen binds to the heme. < <
A variant of hemoglobin (Boston variant; mutation His E7(58)α → Tyr) promotes methemoglobin formation involving the α (alpha) subunits. What is the maximum value of the Hill constant (n) that you could measure for the Boston variant of hemoglobin? log (YO2 / 1 - YO2 ) = log pO2 - logP50 Please break down each step of the Hill equation and explain why the result for n is valid from a logical standpoint.
The T state of hemoglobin is converted to the R state by what event? Select one: The binding of oxygen destabilizes a more planar heme ring which alters the position of the proximal histidine and subsequently, residues between the alß2 interface. а. b. None of these. The binding of oxygen stabilizes a more planar heme ring which alters the position of the proximal proline and subsequently, residues between the alß2 interface. С. d. The binding of oxygen stabilizes a more planar heme ring which alters the position of the proximal histidine and subsequently, residues between the alß2 interface. The binding of oxygen destabilizes a more planar heme ring which alters the position of the proximal proline and subsequently, residues between the alß2 interface. е.
Which of the following mutations would most likely keep the transitions of T state to R state in hemoglobin unchanged, or similar to the transitions that occur in the native molecule? The three-letter codes for amino acids are used, and the numbers following the amino acids designate the amino acid position in the protein. By convention, the original, native amino acid is listed fırst, followed by the mutational change. Choose one: O A. Asp94→Ile94 O B. Tyr42→Phe42 O C. Asp94 Glu94 O D. Tyr42-Gly42
The mutation in hemoglobin at B82 Lys → Asp results in lowered O,-binding affinity compared to normal hemoglobin. B82 is one of the residues that lines the 2,3-BPG binding site (see Figure 7.29; B82 is adjacent to His143). Based on the location of this residue and the differences between Lys and Asp, sug- gest a rationale for the observed reduction in Oz-binding affinity.
A team of biochemists uses genetic engineering to modify the interface region between hemoglobin subunits. The resulting hemoglobin variants exist in solution primarily as αβ dimers (few, if any, α2β2 tetramers form). Are these variants likely to bind oxygen more weakly or more tightly? Explain your answer.

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