2. TERTIARY STRUCTURE OF PROTEINS
Tertiary Structure describes the shapes which form
when the secondary spirals of the protein chain
further fold up on themselves.
The overall three-dimensional arrangement of all
atoms in a protein.

3. DOMAINS are the fundamental functional and three
dimensional structural units of a
polypeptide.Polypeptide chains that are greater than
200 aminoacids in length consists of two or more
domains.
The core of the domain is built from super secondary
elements(motifs)

4. Folding of the peptide chain within a domain usually
occurs independentlay of folding in others domain.
Therefore each domain has a characteristics of a small
compact globular protein that is structurally
independent of the other domains in the polypeptide
chain.

6. Interactions stablizing tertiary structure
The unique three dimensional structure of each
polypeptide is determined by the aminoacid
sequence.Interactions between the side chains of
aminoacids guide the folding of the polypeptide to
form the compact structure .
Four types of interactions cooperate in stablizing the
tertiary structure of globular proteins.

7. Disulfide bond
Hydrophobic interactions
Hydrogen bonds
Ionic interactions

10. QUATERNARY STRUCTURE
 Some proteins contain two or more separate
polypeptide chains or subunits.The arrangement of
these protein subunits in three-dimensional
complexes constitutes quaternary structure.
For example globin of hemoglobin is made up of four
subunit,Enzyme pyruvate dehydrogenase is madeup
of three subunits

11. Protein undergo assisted folding
A specialized group of proteins, named chaperones
are required for the proper folding of many species of
proteins.
Molecular chaperones: Hsp 70, Hsp 40, Dna K, Dna J,
Grp E, chaperonins…etc.
Protein disulfide isomerase (PDI): catalyzes the
interchange or shuffling of disulfide bonds.
Peptide prolyl cis-trans isomerase (PPI): catalyzes the
interconversion of the cis and trans isomers of
proline peptide bonds.

12. Protein misfolding
Protein folding is a complex,trial and error process
that can some times result in improperly folded
molecules.
Deposits of misfolded proteins are associated with a
number of diseases including
1.Amyloidoses
2.Prion disease