2. Some of biochemical functions performed by proteins:
Binding – specific recognition of other molecules
Catalysis – most of the catalysts are proteins
Switching – molecular switches to control cellular processes
Structural proteins – major structural elements of living systems
There is a linear relationship between the DNA base sequence of
a gene and the amino acid sequence of the protein.
4. The Amide/Peptide Bond
Amide/peptide bonds are stable in water at neutral pH and the properties of the peptide bond have
important effects on the stability and flexibility of polypeptide chains in water.
11. Chemical interactions that Stabilize
Proteins
Hydrogen Bond
Ionic Bond
Hydrophobic interactions
van der waals interactions
Disulphide Bond/Bridge
Coulombic interactions
15. The Tertiary structure of
protein
Structure of sperm whale myoglobin – 153 residues folded into 8 alpha
helix
It is the folding of its secondary structural element
16. Structure of the Jack Bean protein – Concanavalin A
Structure of the Human Carbonic anhyydrase
Globular proteins consists of different proportions of α-helix and ß-sheets
The location of side chains varies with polarity: Nonpolar residues in the interior,
Charged polar residues on the surface and Uncharged polar residues on the surface.
Globular proteins are efficiently packed adopting relax conformation.
18. Domains
Immunoglobulin fold
Retinol Binding protein
Domains are two or more globular clusters of approximately 200 residues
Domains are structurally independent units that each have the characteristics of a small globular protein
Domains are classified as α domains (exclusively helices), ß domains (exclusively ß sheets)and α/ ß domains
(containing α helices and ß sheets)
19.
20.
21.
22.
23. Quaternary structure
Many proteins are composed of more than one polypeptide chains called
oligomers
Each polypeptide chain is monomer; dimers-2, trimer-3, tetramer-4,
pentamers-5, hexamers-6
Oligomers composed of only one type of monomers e.g keratin is homotrimer
Oligomers composed of monomers encoded by different genes-heterodimers
24. Intermolecular interactions dependon complementarity
Hydrogen-bond donors are opposite acceptors
Non-polar groups are opposite other non-polar groups
Positive charges are opposite negative charges
Protein –stabilizing interactions contribute to the formation of intermolecular
interfaces e.g hydrophobic interaction, hydrogen bond, salt bridges, disulphide
bond and metal ion ligation occur at the interfaces of protein-protein or
protein-peptidecomplexes.
25. Identical subunits are usually symmetric because in order to interact, each
subunit must possess binding region and its complement
Non-identical subunits form asymmetric complex