Biochem help - In hemoglobin, the distal and proximal histidines

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In summary, the distal and proximal histidines are two amino acid residues in hemoglobin that play crucial roles in stabilizing the iron atom in the heme group, allowing for efficient binding and release of oxygen molecules. They also help to regulate the oxygen release and mutations in these amino acids can disrupt hemoglobin function, leading to conditions such as sickle cell anemia.
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biochem help! -- In hemoglobin, the distal and proximal histidines...

Homework Statement



In hemoglobin, the distal and proximal histidines are critical in the function of the protein, and they are found in both α and β chains. The distal histidine corresponds to position 65 in the alignment and the proximal histidine to position 94 in the alignment. How does the sequence identity around these residues compare to the overall identity? (Consider an 11-residue block centered on the histidine). Briefly explain, in one or two sentences, why this makes sense in terms of protein structure

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The Attempt at a Solution


Would the sequence identity be higher around these histidines because throughout the sequence we want conservative amino acids so the function is not changed? also the amino acids around this should be hydrophobic surrounded by hydrophillic so it get the globular shape?
 
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Dear student,

Thank you for your question. Yes, you are correct in your understanding of the sequence identity around the distal and proximal histidines in hemoglobin. The sequence identity around these residues is usually higher compared to the overall identity because these histidines are crucial for the function of the protein and therefore, any changes in their sequence can affect the protein's ability to bind and transport oxygen.

In terms of protein structure, the higher sequence identity around these histidines makes sense because they are located in the heme binding pocket of the protein. This pocket is hydrophobic and surrounded by hydrophilic residues, which helps to stabilize the heme group and facilitate oxygen binding and release. Any changes in the sequence around these residues could disrupt this delicate balance and affect the protein's ability to function properly.

I hope this helps to clarify your understanding of the importance of the distal and proximal histidines in hemoglobin. Keep up the good work in your studies!
 

Related to Biochem help - In hemoglobin, the distal and proximal histidines

1. What is the role of the distal and proximal histidines in hemoglobin?

The distal and proximal histidines are two amino acid residues located in the heme pocket of hemoglobin. Their main role is to stabilize the iron atom in the heme group, allowing it to bind and release oxygen molecules more efficiently.

2. How do the distal and proximal histidines affect the oxygen binding affinity of hemoglobin?

The distal histidine, located on the same side as the heme group, helps to prevent oxidation of the iron atom, which would decrease the oxygen binding affinity. The proximal histidine, located on the opposite side, helps to stabilize the iron atom in its reduced form, allowing it to bind oxygen more easily.

3. Are the distal and proximal histidines essential for hemoglobin function?

Yes, the distal and proximal histidines play crucial roles in hemoglobin function. Without these amino acids, the heme group would not be properly stabilized, leading to decreased oxygen binding and impaired oxygen transport in the body.

4. Do the distal and proximal histidines have any other functions in hemoglobin?

Aside from their role in stabilizing the heme group, the distal and proximal histidines also play a role in regulating the release of oxygen from hemoglobin. The distal histidine helps to prevent premature release of oxygen, while the proximal histidine allows for efficient release when needed.

5. Can mutations in the distal and proximal histidines affect hemoglobin function?

Yes, mutations in these amino acids can disrupt the proper function of hemoglobin, leading to conditions such as sickle cell anemia. Changes in the distal and proximal histidines can alter the oxygen binding affinity and stability of hemoglobin, affecting its ability to transport oxygen throughout the body.

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