“Structure of Proteins”
Overview
The 20 amino acids commonly found in proteins are
joined together by peptide bonds.
The linear sequence of the linked amino acids contains
the information necessary to generate a protein
molecule with a unique three-dimensional shape.
The complexity of protein structure is best analyzed
by considering the molecule in terms of four
organizational levels:
Primary
Secondary
Tertiary
Quaternary
An examination of these hierarchies of increasing
complexity has revealed that certain structural
elements are repeated in a wide variety of proteins.
This suggests that there are general “rules” regarding
the ways in which proteins achieve their native,
functional form.
thehandynotes.online
, These repeated structural elements range from:
Simple combinations of α-helices and β-sheets
forming small motifs
To the complex folding of polypeptide domains of
multifunctional proteins
Primary Structure of Proteins
The sequence of amino acids in a protein is called the
primary structure of the protein.
Understanding the primary structure of proteins is
important because:
Many genetic diseases result in proteins with
abnormal amino acid sequences
These abnormal sequences cause improper folding
and loss or impairment of normal function
If the primary structures of the normal and the
mutated proteins are known:
This information may be used to diagnose or
study the disease
thehandynotes.online
,A. Peptide Bond
In proteins, amino acids are joined covalently by
peptide bonds
Peptide bonds are:
Amide linkages between the α-carboxyl group of
one amino acid and the α-amino group of another
Example:
Valine and alanine can form the dipeptide
valylalanine through the formation of a peptide
bond
Peptide bonds are not broken by conditions that
denature proteins, such as:
Heating
High concentrations of urea
Prolonged exposure to a strong acid or base at
elevated temperatures is required to hydrolyze these
bonds nonenzymically
thehandynotes.online
, Naming and Characteristics of Peptides
1. Naming the Peptide
By convention:
The free amino end (N-terminal) of the peptide
chain is written to the left
The free carboxyl end (C-terminal) is written to
the right
Therefore, all amino acid sequences are read from the
N- to the C-terminal end of the peptide.
Linkage of many amino acids through peptide bonds
results in an unbranched chain called a polypeptide
Each component amino acid in a polypeptide is called a
“residue”:
This is because it is the portion of the amino acid
remaining after the atoms of water are lost in
the formation of the peptide bond.
thehandynotes.online
Overview
The 20 amino acids commonly found in proteins are
joined together by peptide bonds.
The linear sequence of the linked amino acids contains
the information necessary to generate a protein
molecule with a unique three-dimensional shape.
The complexity of protein structure is best analyzed
by considering the molecule in terms of four
organizational levels:
Primary
Secondary
Tertiary
Quaternary
An examination of these hierarchies of increasing
complexity has revealed that certain structural
elements are repeated in a wide variety of proteins.
This suggests that there are general “rules” regarding
the ways in which proteins achieve their native,
functional form.
thehandynotes.online
, These repeated structural elements range from:
Simple combinations of α-helices and β-sheets
forming small motifs
To the complex folding of polypeptide domains of
multifunctional proteins
Primary Structure of Proteins
The sequence of amino acids in a protein is called the
primary structure of the protein.
Understanding the primary structure of proteins is
important because:
Many genetic diseases result in proteins with
abnormal amino acid sequences
These abnormal sequences cause improper folding
and loss or impairment of normal function
If the primary structures of the normal and the
mutated proteins are known:
This information may be used to diagnose or
study the disease
thehandynotes.online
,A. Peptide Bond
In proteins, amino acids are joined covalently by
peptide bonds
Peptide bonds are:
Amide linkages between the α-carboxyl group of
one amino acid and the α-amino group of another
Example:
Valine and alanine can form the dipeptide
valylalanine through the formation of a peptide
bond
Peptide bonds are not broken by conditions that
denature proteins, such as:
Heating
High concentrations of urea
Prolonged exposure to a strong acid or base at
elevated temperatures is required to hydrolyze these
bonds nonenzymically
thehandynotes.online
, Naming and Characteristics of Peptides
1. Naming the Peptide
By convention:
The free amino end (N-terminal) of the peptide
chain is written to the left
The free carboxyl end (C-terminal) is written to
the right
Therefore, all amino acid sequences are read from the
N- to the C-terminal end of the peptide.
Linkage of many amino acids through peptide bonds
results in an unbranched chain called a polypeptide
Each component amino acid in a polypeptide is called a
“residue”:
This is because it is the portion of the amino acid
remaining after the atoms of water are lost in
the formation of the peptide bond.
thehandynotes.online
