In terms of the structural aspects of Hb that we discussed in class, explain asmany features of the...

Question

In terms of the structural aspects of Hb that we discussed in class, explain asmany features of the following Hb variants as you can (you may not be able toexplain all of the properties).
Sketch an O2 binding curve for each variant,comparing it to Mb and HbA curves. The columns, O2 affinity, Bohr effect, Hillcoef. (coefficient) and BPG effect, refer to that property of the variant comparedto normal HbA at neutral pH with 0.1 M NaCl (“normal” conditions). Also,indicate how the affected subunit would change the electrophoretic mobility ofthe Hb tetramer in non-denaturing native electrophoresis.

a.Variant: Hb Hiroshimaß146 His->Asp
Bohr effect: reducedO2 affinity: increasedHill coef: 2.0BPG effect: decreased
b.Variant:Hb Bassetta94 Asp->Ala
O2 affinity: reducedBohr effect: reducedHill coef: 1.4BPG effect: normal

David · Accepted Answer

Part a: 
Variant: Hb Hiroshima: 
Features of Hb Hiroshima: 
In this variant 146 histidine residue in beta chain is replaced by aspartate. The point mutation in 
Hb Hiroshima has affected three of the important properties of oxygen hemoglobin saturation 
process: 
 • Heme-heme interaction: 
The cooperative binding properties of hemoglobin depend on interactions between the alpha and 
beta subunits and the binding of oxygen is mediated by dissociation of the tetrameric molecule 
into two symmetric dimmers accompanied by subunit exchange. This mutation interferes with 
interactions between unlike subunits and impairs heme-heme interaction and reduces the Bohr 
(pH) effect. 
 • Hill coefficient is determined by cooperativity, as the mutation decreases 
the cooperativity, it also reduces hill coefficient than HbA. 
 • BPG combines reversibly with normal hemoglobin in equimolar amounts 
of oxygen, thus BPG reduces the affinity of hemoglobin for oxygen by blocking its 
binding site. In this variant the mutation of single amino acid reduces the affinity of 
hemoglobin for BPG.

In terms of the structural aspects of Hb that we discussed in class, explain asmany features of the following Hb variants as you can (you may not be able toexplain all of the properties). Sketch an O2...

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