protein structure and level
of protein structure
IZZEDDIN HALAWA
Master biology
speclization in molecular
genetics and cell biology
protein structure
• polymer of aminoacid mad up of one or more
polypeptidechain
• every protein in its native state has three dimentional
stricture which refere to as conformation .
• the number and the seqouence of these amio acid in
protein are diferent
• the fuction of protein arise from it is conformation
• protein structure classified into four level of
orgnaization
Degree of complexity
Four Levels of Protein Structure
Four Levels of Protein
Structure
• Primary Structure:
Linear Sequence of Amino Acids
O
H
H2N
C
R
C
OH
amio acids
• Amino acids are the monomers that make up
proteins. Each amino acid has the same
fundamental structure , which consists of a central
carbon atom, also known as the alpha (α) carbon,
bonded to an amino group (NH2), a carboxyl group
(COOH), and to a hydrogen atom
.
amino acid structure
The carboxyl group of one amino acid is linked
to the amino group of the next amino acid.
Four Levels of Protein
Structure
• Primary Structure:
Amino Acids are linked with a covalent
bond called a peptide bond.
H2N
H
O H
H
C
C
N
C
R1
R2
O
C
OH
Four Levels of Protein Structure
• Secondary Structure:
Folded structure due to hydrogen bonds
between the amino and acid groups of
amino acids
N
C
N
C
H
O
H
O
O
H
O
H
C
N
C
N
or
Four Levels of Protein Structure
• Tertiary Structure:
Three dimensional folded structure due to
attractions and repulsions between R
groups
All but peptide bonds are
involved in tertiary structure.
Four Levels of Protein Structure
• Quaternary structure:
Association of two or more protein
chains
eg. Hemoglobin is composed of
4 protein chains
2 are called alpha hemoglobin
2 are called beta hemoglobin
Protein folding
• the process by which a protein structure
assumes its functional shape or
conformation.
• All protein molecules are heterogeneous
unbranched chains of amino acids. By
coiling and folding into a specific threedimensional shape they are able to perform
their biological function.
chaperones
• chaperones are proteins that assist the
conformational folding or unfolding and the
assembly or disassembly of other macromolecular
structures.
• major function of chaperones is to prevent both
newly synthesised polypeptide chains and
assembled subunits from aggregating into
nonfunctional structures.
Neurodegenerative Diseases
• In neurodegenerative diseases such as Alzheimer's disease
and transmissible spongiform encephalopathy (mad cow),
insoluble misfolded proteins accumulate in the brain in
pathological lesions known as plaques, resulting in
neurodegeneration.
• In Alzheimer's disease, the protein known as amyloid
precursor protein is cleaved into a peptide product (bamyloid) that aggregates and precipitates in amyloid
filaments.
• The misfolding of b-amyloid, which involves a transition from
a helical to b sheet conformation leads to filament formation.
In mad cow disease, prion proteins precipitate causing
lesions.
the End
thank for your attention