Determine the primary structure of an octapeptide from the...

Determine the primary structure of an octapeptide from the following data: Acid hydrolysis gives 2 Arg, Leu, Lys, Met, Phe, Ser, Tyr. Carboxypeptidase A releases Ser. Edman's reagent releases Leu. Cyanogen bromide forms two peptides with the following amino acid compositions: 1. Arg, Phe, Ser 2. Arg, Leu, Lys, Met, Tyr Trypsin forms the following two peptides and two amino acids: 1. Arg 2. Ser 3. Arg, Met, Phe 4. Leu, Lys, Tyr

Determine the primary structure of an octapeptide from the following data:
Acid hydrolysis gives 2 Arg, Leu, Lys, Met, Phe, Ser, Tyr.
Carboxypeptidase A releases Ser.
Edman's reagent releases Leu.
Cyanogen bromide forms two peptides with the following amino acid compositions:
1. Arg, Phe, Ser
2. Arg, Leu, Lys, Met, Tyr
Trypsin forms the following two peptides and two amino acids:
1. Arg
2. Ser
3. Arg, Met, Phe
4. Leu, Lys, Tyr

Key Concepts

Primary Structure of Proteins

The primary structure is the linear sequence of amino acids in a peptide or protein, specifying its exact order from the N?terminus to the C?terminus. Determining the primary structure is fundamental to understanding protein function, as it dictates how the protein folds and interacts with other molecules.

Amino Acid Composition Analysis (Acid Hydrolysis)

Acid hydrolysis is a method used to break a peptide or protein into its constituent amino acids. By analyzing the resulting amino acid composition, one can determine which residues are present and in what stoichiometric amounts, providing an overall ‘inventory’ that must be consistent with any proposed primary structure.

Exopeptidase Specificity (Carboxypeptidase A Release)

Exopeptidases such as carboxypeptidase A cleave amino acids sequentially from the end of a peptide chain. Carboxypeptidase A, which removes residues from the C?terminus, can help identify the identity of the terminal amino acid, a critical clue in establishing the peptide’s sequence.

N?terminal Sequencing (Edman Degradation)

Edman degradation is a stepwise chemical method used to sequence amino acids from the N?terminus of a peptide. By sequentially identifying each amino acid, this technique provides direct information about the starting residue and the order of residues at the beginning of the sequence.

Specific Chemical Cleavage (Cyanogen Bromide)

Cyanogen bromide reacts specifically with methionine residues in peptides, cleaving the peptide bond on the carboxyl side of methionine. The resulting peptide fragments, with their known amino acid compositions, offer valuable information regarding the position of methionine and the segmentation of the overall sequence.

Enzymatic Cleavage Specificity (Trypsin Digestion)

Trypsin is a proteolytic enzyme that cleaves peptides on the carboxyl side of lysine and arginine residues, except when followed by proline. The pattern of fragments produced by trypsin digestion, including the lengths and sequences of the released peptides as well as any free amino acids, is exploited to deduce the positions of these basic residues in the original sequence.

Integration of Cleavage Data (Fragment Mapping)

By combining information from different cleavage procedures—chemical and enzymatic—a complete map of the peptide can be constructed. Each method provides overlapping pieces of sequence information, and when these fragments are integrated, the order of the amino acids in the entire peptide chain can be deduced.

Transcript

00:02 The problem contains an octa peptide.

00:10 So the octa peptide we have 1, 2, 3, 4, 5, 6, 7, 8.

00:32 In which the n terminal is l .eu.

00:43 So the edmund reagent, that man reels l -p -u as the n terminal so we put l -p -u here carboxy bacteries gives the the c terminal so c terminal and carboxy bacteria releases s -e -r serene so the c terminal remember this is the n side and this is the n -terror terminal always peptides are written with the end terminal on the left side and c terminal on the right end side so c terminal.

01:49 Now let us look at what cyanogen bromide do.

01:55 Cyanogen bromide hydrolysis the c -1cionide cyanbronide c -n -br hydrolyse hydro -nice c -side.

02:16 Now in the given data in the given data, methionine is contained in a polypeptide having one, two, three, four, five amino acids, in which l u is present.

02:41 That means from here fifth amino acid is methyonine.

02:49 Now in between we have thyrin, lycine and arson, thyrusin, lycine and arson.

03:05 These are there in between we are to find out the order on the other side we have s -e -r -a -r -g -p -h -e so s -er -g is here now we have a -r -g -g and p -h -e here okay now next tripsin catalytic hydrolysis forms the two amino acids and two peptides so tripsin catalyze what does the trypsin do that is a lot that is no doubt that tripsin will hydrolyse the sea side of arginine and lysine tripsin will hydrolyte hydrolyte sea side of arginine sea side of arginine and lysine so that means here there is licein now licein containing peptide let us look at the lysine containing peptide so where is lysinease.

04:45 So the lysine containing peptide is lys l -e -u -t -y -r...

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