The document discusses the primary structure of proteins, which refers to the specific sequence of amino acids in a polypeptide chain. Amino acids are linked together by peptide bonds to form the primary structure. The different arrangements of amino acids give rise to different protein structures and functions. The primary structure determines the overall shape and conformation of a protein.

1. Primary
Structure
of
Protein

2.  Primary structureofproteinrefers tothesequence of
aminoacidspresent ina polypeptidechain.
 Aminoacidsare covalentlylinkedby peptidebond.
 Each componentin aminoacid ina polypeptideis called
“residue”.
 Thedifferentarrangementofaminoacidsyielddifferent
structure withdifferentfunctionsand activities.
 It determinestheshapeor conformation,intowhich a
proteincan bearranged.

3.  Methionineenkephalin
◦ Try-Gly-Gly-Phe-Leu
 Leucineenkephalin
◦ Try-Gly-Gly-Phe-Leu

4.  To predict the 2nd and 3rd structure from sequence
homologies withrelated proteins.
 Many geneticdiseases result from abnormal amino
acid sequences.
 To understandthe molecular mechanismof action in
protein.
 To trace evolutionary paths.

5.  Insulin– the first protein in which the sequenceof
amino acids was determined.
 some insulinfrom animals is biologically active in
humansand can be used for treatment.
And insulinfrom humans,differs slightlyby one, two, or
three aminoresidues in chain A.

7.  The regulararrangementor coilingofsegmentsofprotein
chains.
 A uniquethree-dimensionalshapeofeach proteinwhich is
importanttoitsfunction. Itis theconformationor the shape
ina relativelysmallor localizedregion ofa polypeptide
molecule.
 Secondary structures haverepetitiveinteractionresulting
fromhydrogen binding betweentheamideN – H and the
carbonylgroups of thepeptidebackbones.

8. α Helix
•Coiling of the protein chain in the shape of a
right-handed helix.
e.g α keratin.
•The C=O oxygen of anamino acid residue is
H-bonded to the N-H hydrogen of the 4th
amino acidresiding further down the
polypeptide chain.

9. α- Helix

10.  β pleated sheet – a side by side alignment of adjacent polypeptide
chains.
◦ H- bondingoccurs betweenC=O oxygenofone chainandtheN-Hhydrogenofan
adjacent.
Thesheet conformation permits the stacking of sheets one ontop of the other.

11. Two Types ofβpleated sheet

12.  β bends – permits the
changein direction of
a peptide chain to get a
folded structure.
- It gives proteins
globularity rather than
linearity.

13.  TripleHelix – right handedsuper helix
by the right-handed coiling of three
polypeptide chain.
 Collagen– most abundant protein in
mammals.
- Constitutes the major portion of tendons
and ligaments.
- Important constituent ofskin.
 Vitamin Cis required in the formation of
collagen, particularly in the hydroxylation
of proline to form hydroxyproline to
stabilize the structure ofcollagen.