Here is the amino acid sequence for bovine casein, using the one letter amino ac
ID: 59162 • Letter: H
Question
Here is the amino acid sequence for bovine casein, using the one letter amino acid codes.
MKVLILACLVALALARELEELNVPGEIVESLSSSEESITRINKKIEKFQSEEQ
QQTEDELQDKIHPFAQTQSLVYPFPGPIPNSLPQNIPPLTQTPVVVPPFLQPE
VMGVSKVKEAMAPKHKEMPFPKYPVEPFTESQSLTLTDVENLHLPLPLLQSWM
HQPHQPLPPTVMFPPQSVLSLSQSKVLPVPQKAVPYPQRDMPIQAFLLYQEPV
LGPVRGPFPIIV
Put a box around any residues that will have a positively charged side chain at a pH equal
to the pI value that you determined.
Put a circle around any residues that will have a negatively charged side chain at a pH
equal to the pI value that you determined.
Is this sequence consistent with the pI value that you determined? Explain why or why not.
Explanation / Answer
pI = pKa1 + pKa2 / 2
For this protein, the pI value comes out to be 5.7
So, pH = 5.7
Lets calculate the net charge on the protein at this pH
Total positively charged residues = 4 (R) + 12 (K) = 16
Total negatively charged residues = [ - 4 (D)] + [- 19 (E)] = - 23
Therefore, net charge of protein = - 7
or protein is negatively charged
The isoelectric point (pI), is the pH at which a particular molecule carries no net electrical charge.
So, this sequence is not consistent with the pI value that was determined