Q.19 The number of fragments generated when the peptide
‘ANDCQEGKFMLKPDTWRYVSFMRPA’ is subjected to complete digestion with trypsin are ……
6 fragments are generated from complete trypsin digestion of the peptide ‘ANDCQEGKFMLKPDTWRYVSFMRPA’. Trypsin cleaves at the C-terminal side of lysine (K) and arginine (R), unless followed by proline (P).
Trypsin Cleavage Rules
Trypsin specifically hydrolyzes peptide bonds after K or R residues. Cleavage does not occur if P immediately follows, as in K-P or R-P bonds, due to steric hindrance.
Sequence Analysis
The peptide sequence is A-N-D-C-Q-E-G-K-F-M-L-K-P-D-T-W-R-Y-V-S-F-M-R-P-A (24 amino acids).
Cleavage sites (after K/R not followed by P):
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Position 8: K (followed by F → cleaves)
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Position 12: K (followed by P → no cleavage)
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Position 18: R (followed by Y → cleaves)
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Position 22: R (followed by P → no cleavage)
Generated Fragments
Cuts after positions 8 and 18 produce these fragments:
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ANDCQEGK (1-8)
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FMLKP (9-13)
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DTWR (14-17)
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YVSFMR (18-23)
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PA (24)
No: wait, positions: let’s number 1=A,2=N,…,8=K,9=F,10=M,11=L,12=K,13=P,14=D,15=T,16=W,17=R,18=Y? Wait, sequence: ANDCQEGK F M L K P D T W R Y V S F M R P A
Positions:
1A 2N 3D 4C 5Q 6E 7G 8K |cut| 9F 10M 11L 12K 13P 14D 15T 16W 17R |cut| 18Y 19V 20S 21F 22M 23R 24P? Wait, sequence is ANDCQEGKFMLKPDTWRYVSFMRPA
Let’s list correctly:
Position: Amino acid
1: A
2: N
3: D
4: C
5: Q
6: E
7: G
8: K
9: F
10: M
11: L
12: K
13: P
14: D
15: T
16: W
17: R
18: Y
19: V
20: S
21: F
22: M
23: R
24: P
25: A Wait, count letters: A N D C Q E G K F M L K P D T W R Y V S F M R P A
That’s 25 letters! A(1)N(2)D(3)C(4)Q(5)E(6)G(
