The side chain of histidine has a typical pK a value in the range of 6.5-7.4. Ho
ID: 979543 • Letter: T
Question
The side chain of histidine has a typical pKa value in the range of 6.5-7.4. However, when analyzing the pKa values in a particular protein, scientists determined that one particular His residue has an unusually low pKa value of 4.8. Which of the following statements correctly explain this anomaly?
1) The microenvironment around a residue can impact its pKa value.
2) A positively charged amino acid must be in close proximity to this residue.
3) A negatively charged amino acid must be in close proximity to this residue.
4) This residue must be located on the surface of the protein.
The side chain of histidine has a typical pKa value in the range of 6.5-7.4. However, when analyzing the pKa values in a particular protein, scientists determined that one particular His residue has an unusually low pKa value of 4.8. Which of the following statements correctly explain this anomaly?
1) The microenvironment around a residue can impact its pKa value.
2) A positively charged amino acid must be in close proximity to this residue.
3) A negatively charged amino acid must be in close proximity to this residue.
4) This residue must be located on the surface of the protein.
Explanation / Answer
Statements 1 and 2 are correct.
1) The microenvironment around a residue can impact its pKa value.
2) A positively charged amino acid must be in close proximity to this residue.
In microenvironment around one amino acid group effects the pKa of the resdue..
When a positively charged amino acid is in close proximity, pKa of residue will be lowered.
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