Hemoglobin (Hb) is the essential O2 transporter in adult humans that carries oxygen from the lungs to peripheral tissues where it is needed for oxidative respiration.As you might imagine, amino acid substitutions in Hb that lead to dysfunction can have rather significant physiological effects. Perhaps surprisingly, there are more than 1,000 naturally occurring Hb variants (Hb genes that encode proteins with amino acid substitutions) that alter its structure and biochemical properties resulting in mild to severe pathologies. In addition, tissue, organismal, and developmental stage specific Hb can be expressed to suit the needs of the organism. Here you will explore an Hb variant of your choosing and discuss the biochemical effects of this substitution on: 1) Hb-O2 binding affinity and cooperativity, 2) allostery, 3) and human physiology.
Respond to each of the following items thoroughly, but concisely. Most of the questions have multiple parts; be sure to provide an answer for each of them. An excellent response will include details from the literature and course content to accurately describe the effect of your amino acid substitution on Hb function and physiology.
provide your response directly on this document. The amount of space provided for each question does not reflect the suggested amount of space needed to provide an excellent response. Please provide references for any relevant information that you obtain from the literature.
choose an Hb variant from the literature. This should be a variant that has been characterized biochemically and physiologically (and perhaps structurally). This can include a naturally occurring Hb that contains an amino acid substitution, or a tissue or organism specific Hb that displays altered biochemical properties relative to adult human Hb. Please provide the name and a reference for your Hb variant below.
Describe how this variant was identified, or what special role it plays in normal physiology.
What amino acid substitution does your Hb variant express? Describe the chemical features of the original and variant amino acids.
In which region of the Hb tetramer structure does this substitution occur? I.e. at the α1-β1 interface, the α1-β2 interface, the O2 binding pocket, the Heme binding pocket, the hydrophobic core, etc.?Describe how you think this substitution might affect Hb function based on its location in the tetramer structure. How does this relate to topics that we discussed in class regarding Hb function?
describe the biochemical effects of your amino acid substitution. I.e. does it lead to a reduction in O2 binding affinity, cooperativity, relaxed allostery, etc.? Do these biochemical effects make sense given what you know about the chemical nature of the substitution and the structure and function of Hb?
What is the clinical impact of this substation on human physiology? Is this a severe or mild phenotype? What are the available treatments associated with this variant and what are their mechanisms of action? Please be as detailed as possible here.
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