This document discusses the different levels of protein structure: primary, secondary, tertiary, and quaternary. The primary structure refers to the amino acid sequence. Secondary structure involves local folding into alpha helices or beta sheets. Tertiary structure describes the overall 3D shape of a single polypeptide chain. Quaternary structure refers to the arrangement of multiple polypeptide subunits in a multimeric protein. Recent discoveries are mentioned about determining the structures of specific proteins and learning more about their functions.

1. Presented By:
SATYA PRAKASH RANJAN
MCA/25005/18

2. CONTENTS
INTRODUCTION TO PROTEIN
STRUCTURE
PRIMARY STRUCTURE
SECONDARY STRUCTURE
TERTIARY STRUCTURE
QUATERNARY STRUCTURE

3. By,
SATYA PRAKASH RANJAN

4. • Proteins are an important class of
biological macromolecules
which are the polymers of amino
acids.
• Biochemists have distinguished
several levels of structural
organization of proteins. They
are:
– Primary structure
– Secondary structure
– Tertiary structure
– Quaternary structure
INTRODUCTION

5. PRIMARY STRUCTURE
• The primary structure of protein refers to the sequence of amino
acids present in the polypeptide chain.
• Amino acids are covalently linked by peptide bonds.
• Each component amino acid in a polypeptide is called a “residue” or
“moiety”

6. SECONDARY STRUCTURE
• Localized arrangement of adjacent amino acids formed as the polypeptide
chain folds.
• Types of secondary structure
α-helix
β-pleated sheet

7. • Spiral structure
• Tightly packed, coiled polypeptide
backbone core.
• Side chain extend outwards
• Stabilized by H bonding b/w
carbonyl oxygen and amide
hydrogen.
• Alpha helical segments are found in
many globular proteins like
myoglobins, troponin- C etc.
ALPHA HELIX
H bonding

8. BETA PLEATED SHEET
• Formed when 2 or more polypeptides
line up side by side.
• Individual polypeptide - β strand
• Each β strand is fully extended.
• They are stabilized by H bond b/w N-H
and carbonyl grps of adjacent chains.
2 types
Parallel Anti -Parallel
N
N
C
C
C
N
N
C

9. TERTIARY STRUCTURE
• Tertiary structure is the three-
dimensional conformation of a
polypeptide.
• The common features of protein
tertiary structure reveal much about
the biological functions of the proteins
and their evolutionary origins.
• The function of a protein depends on
its tertiary structure. If this is disrupted,
it loses its activity.

10. • Polypeptide chains containing more than ,200 residues usually
fold into two or more globular clusters known as domains.
• Fundamental functional and 3 dimensional structure of
proteins.
• Domains often have a specific function such as the binding of
a small molecule.
• Many domains are structurally independent units that have the
characteristics of small globular proteins.
The two-domain protein glyceraldehyde-
3-phosphate dehydrogenase.
NAD+

11. • The biological function of some
molecules is determined by multiple
polypeptide chains –
multimeric proteins.
• Arrangement of polypeptide sub unit
is called quaternary structure.
• Sub units are held together by non
covalent interactions.
• Eg: Hemoglobin has the subunit
composition a2b2
QUATERNARY STRUCTURE
Quaternary structure of hemoglobin.

12. RECENT DEVELOPMENTS
• A team of scientists at The Scripps Research Institute and the
National Institutes of Health (NIH) has discovered the
structure of a protein – dynamin, that pinches off tiny pouches
from cell’s outer membranes.
• Scientists at the Institute of Structural and MolecularBiology
have revealed the structure of a complex protein called FimD
that acts as an assembly platform for the pili of cystitis
bacteria.
• Researchers from the Walter and Eliza Hall Institute have
found a structural surprise in a type of protein, Bcl-w ,that
encourages cell survival, raising interesting questions about
how the proteins function to influence programmed cell death.

13. CONCLUSION
• Proteins are extraordinarily complex molecules. Of all the
molecules encountered in living organisms, proteins have the
most diverse functions.
• So a basic understanding of the structure of proteins is
necessary to comprehend its role in organisms.
• Further researches will provide more insight into the structure
of several other proteins in the coming year.

14. REFERENCE
• https://www.khanacademy.org/science/biology/macromo
lecules/proteins-and-amino-acids/a/orders-of-protein-
structure?utm_account=Grant&utm_campaignname=Gra
nt_Science_Dynamic&gclid=Cj0KCQjw7sDlBRC9ARIsAD-
pDFrIMCZxtuUDmbRmMkoVppDrxrkBpIZh64xit8bD9jK
-jgh93cCE2zwaArahEALw_wcB
• step. closer. with. discovery. protein. structure
• https://wp.nyu.edu/
step.closer.with.discovery.bacterial.protein.structure
• https://www.youtube.com/watch?v=FkjilyNaT3
M s
• Channel name shomu’s biology

15. THANK YOU