9. Two bands are extracted from an electrophoresis gel, corresponding to two dif

Question

9. Two bands are extracted from an electrophoresis gel, corresponding to two different polypeptides (A and B). In order to sequence, them they were each individually subjected to digestion by two different proteases: chymotrypsin and S. aureus V8 protease. The resulting smaller peptides were then sequenced. From the following results of each digestion, give the full sequence for the A and B polypeptides. Explain your results. Cleavage with chymotrypsin produces the following fragments: BAND A CN NLQNY GIVEQCCHKRCSEY BAND B F DPTKM ACGVRGF RTTGHLCGKDLVNALY Cleavage with S. aureus V8 proteases produces the following fragments: BAND A GIVE YNLQNYCN QCCHKRCSE BAND B PTKM RTTGHLCGKD LVNALYIACGVRGFFYD

Explanation / Answer

Question 9:

Chymotrypsin cleaves the carboxyl side of the aromatic amino acids such as Phenylalanine (F), Tryptophan (W), and Tyrosine (Y).

S. aureus V8 protease cleaves the carboxyl side of Glutamic acid (E) and Aspartic acid (D).

Determination of the full sequence of the polypeptide A:

Cleavage with chymotrypsin produces the following fragments for BAND A:

CN

NLQNY

GIVEQCCHKRCSEY

Cleavage with S. aureus V8 protease produces the following fragments for BAND A:

GIVE

YNLQNYCN

QCCHKRCSE

As chymotrypsin cleaves the carboxyl side of the aromatic amino acids such as Phenylalanine (F), Tryptophan (W), and Tyrosine (Y) and S. aureus V8 protease cleaves the carboxyl side of Glutamic acid (E) and Aspartic acid (D).

Here for polypeptide A, chymotrypsin cleaves the carboxyl side of the Tyrosine (Y) while S. aureus V8 protease cleaves the carboxyl side of the Glutamic acid (E).

Therefore, the full sequence for polypeptide A should be GIVEQCCHKRCSEYNLQNYCN

Determination of the full sequence of the polypeptide B:

Cleavage with chymotrypsin produces the following fragments for BAND B:

F

Y

DPTKM

IACGVRGF

RTTGHLCGKDLVNALY

Cleavage with S. aureus V8 protease produces the following fragments for BAND B:

PTKM

RTTGHLCGKD

LVNALYIACGVRGFFYD

As chymotrypsin cleaves the carboxyl side of the aromatic amino acids such as Phenylalanine (F), Tryptophan (W), and Tyrosine (Y) and S. aureus V8 protease cleaves the carboxyl side of Glutamic acid (E) and Aspartic acid (D).

Here for polypeptide B, chymotrypsin cleaves the carboxyl side of the Tyrosine (Y) and Phenylalanine (F) while S. aureus V8 protease cleaves the carboxyl side of the Aspartic acid (D).

Therefore, the full sequence for polypeptide B should be RTTGHLCGKDLVNALYIACGVRGFFYDPTKM

Related Questions

Navigate

• Browse (All)
• Browse 9
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.