Chapter 21, Problem 38P

$\alpha -$ Cobratoxin is a neurotoxin found in the venom of the Chinese cobra, Najaatra, a prevalent venomous snake that inhabits China and Taiwan. A partial sequence of its 71 amino acid chain is shown.
a. How many amide bonds join the amino acids in the peptide chain?
b.Give the name of the N-terminal amino acid.
c.Give the name of the C-terminal amino acid.

Interpretation Introduction

(a)

Interpretation:

The number of amide bonds that join the amino acids in the: IRCFITPDIT-51 amino acid-CNPFPTRKRP peptide chain.

Concept Introduction:

Amino acids are organic compounds containing two functional groups namely amino and carboxylic group. The amino group is attached to the alpha carbon, carbon adjacent to the carbonyl group making them alpha-amino acids.

Answer to Problem 38P

There are $70$ amide bonds present in the given sequence IRCFITPDIT-51 amino acid-CNPFPTRKRP.

Explanation of Solution

When amino acids joined to one another by amide bonds to form large molecules are called peptides. The amide bonds present in peptides are called peptides bonds.

To make a dipeptide, the amino group $\left({\text{NH}}_{\text{3}}{}^{+}\right)$ of one amino acid joined to the carboxylate group $\left({\text{COO}}^{-}\right)$ of another amino group with the removal of water molecules. Only one amide bond will be there in dipeptide.

To calculate the number of amide bonds present in any sequence will be one less the number of amino acids present in the sequence.

For example, there are two amino acids present in a dipeptide. Then, the number of amide bonds will be one.

The given sequence is as follows:

IRCFITPDIT-51 amino acid-CNPFPTRKRP

There are total $71$ amino acids as $\left(10+51+10\right)$ present in the given sequence. Then, the number of amide bonds will be one less the number of amino acids present in the sequence. Therefore, $70$ amide bonds are present in the given sequence.

Interpretation Introduction

(b)

Interpretation:

The name of the N-terminal amino acid of the given amino acid sequence present in the bee venom should be determined.

IRCFITPDIT-51 amino acid-CNPFPTRKRP

Concept Introduction:

Amino acids are organic compounds containing two functional groups namely amino and carboxylic group. The amino group is attached to the alpha carbon, carbon adjacent to the carbonyl group making them alpha-amino acids.

Answer to Problem 38P

Isoleucine (I) will be the N-terminal amino acid present in the given sequence IRCFITPDIT-51amino acid-CNPFPTRKRP.

Explanation of Solution

Amino acid having a free ${\text{NH}}_{\text{3}}{}^{+}$ group at the alpha (a) carbon is termed as N-terminal amino acid which is always present at the left end of the sequence.

The name, one-letter and three-letter abbreviation of the amino acids are mentioned in the table given below:

Name of Amino Acid	Three-letter abbreviation	One-letter abbreviation
Alanine	Ala	A
Asparagine	Asn	N
Cysteine	Cys	C
Glutamine	Gln	Q
Glycine	Gly	G
Isoleucine	Ile	I
Leucine	Leu	L
Methionine	Met	M
Phenylalanine	Phe	F
Proline	Pro	P
Serine	Ser	S
Threonine	Thr	T
Tryptophan	Trp	W
Tyrosine	Tyr	Y
Valine	Val	V
Aspartic acid	Asp	D
Glutamic acid	Glu	E
Arginine	Arg	R
Histidine	His	H
Lysine	Lys	K

The given sequence is as follows:

IRCFITPDIT-51 amino acid-CNPFPTRKRP

From the table, 'I' will be the amino acid present at the N-terminal. And 'I' is the 'Isoleucine' amino acid.

Interpretation Introduction

(c)

Interpretation:

The name of the C-terminal amino acid of the given amino acid sequence present in the bee venom should be determined.

IRCFITPDIT-51 amino acid-CNPFPTRKRP

Concept Introduction:

Amino acids are organic compounds containing two functional groups namely amino and carboxylic group. The amino group is attached to the alpha carbon, carbon adjacent to the carbonyl group making them alpha-amino acids.

Answer to Problem 38P

Proline (P) will be the C-terminal amino acid present in the given sequence IRCFITPDIT-51amino acid-CNPFPTRKRP.

Explanation of Solution

Amino acid having a free ${\text{COO}}^{-}$ group at the alpha (a) carbon is termed as C-terminal amino acid which is always present at the right end of the chain.

The name, one-letter and three-letter abbreviation of the amino acids are mentioned in the table given below:

Name of Amino Acid	Three-letter abbreviation	One-letter abbreviation
Alanine	Ala	A
Asparagine	Asn	N
Cysteine	Cys	C
Glutamine	Gln	Q
Glycine	Gly	G
Isoleucine	Ile	I
Leucine	Leu	L
Methionine	Met	M
Phenylalanine	Phe	F
Proline	Pro	P
Serine	Ser	S
Threonine	Thr	T
Tryptophan	Trp	W
Tyrosine	Tyr	Y
Valine	Val	V
Aspartic acid	Asp	D
Glutamic acid	Glu	E
Arginine	Arg	R
Histidine	His	H
Lysine	Lys	K

The given sequence is as follows:

IRCFITPDIT-51amino acid-CNPFPTRKRP

From the table, 'P' will be the amino acid present at the C-terminal. And 'P' is the 'Proline' amino acid.