You have discovered a novel protein that has a pl = 5.5. To study the functional
ID: 873981 • Letter: Y
Question
You have discovered a novel protein that has a pl = 5.5. To study the functional properties of this new protein, your research group has made a mutant that contains two amino acid changes-namely, a surface Phe residue in the normal protein has been replaced by His (side chain pKa = 6.1), and a surface GIn has been replaced by Glu (side chain pKa =6.0). Part A Is the pl of the mutant protein predicted to be greater than, less than, or the same as the pl of the normal protein? The pl of the mutant protein predicted to be greater than the pl of the normal protein. The pl of the mutant protein predicted to be the same as the pl of the normal protein. The pl of the mutant protein predicted to be less than the pl of the normal protein.Explanation / Answer
Aminoacid
pKa side chain
Ka
Phe
No relevant side chain
His
6.1
7.9x10-7
Gln
No relevant side chain
Glu
6.0
1.0x 10-6
I = SQRT (Kw
Aminoacid
pKa side chain
Ka
Phe
No relevant side chain
His
6.1
7.9x10-7
Gln
No relevant side chain
Glu
6.0
1.0x 10-6