Transcript bioinformatics lec10student

Chemical and physical
features of proteins
2
+
3
Important terms
ISOELECTRIC POINT (pI) •
ISOIONIC point •
Protein classification
according to the size
Classification of protein
according to the size
Fewer than 50 aa called peptide
More than 50 is called protein
Insulin is 53 aa long
Is it a peptide or protein hormone?
Protein sequence and
structure
The protein seq can be directly retrieved from
the corresponding gene sequence?
True
False
Protein primary structure
Amino acids are attached by
……………………….
These bonds are both planner and
rigid
Can they rotate about their axis?
Protein secondary structure
Stabilized by hydrogen bonding
and depends on the sequence of
aa in the chain
Protein secondary structure
Some amino acids disrupt the
secondary alpha helix structure :
Proline, isoleucin, tryptophan,
asparagine
Do all proteins have
secondary structures?
Yes
No
Tertiary structure
Stabilized by many types of bonds
-electrostatic bonds (-ve & +ve)
-Van der waals forces
-hydrophobic or hydrophillic attractions
Hbonds
Disulfide bridges
Quaternary structure
All proteins do posses quaternary
structure?
True
False
Quaternary structure
More than one polypeptide chains
come together to form quaternary
structure
( we call the protein oligomeric)
Quaternary structure
Stabilized by the same types of bonds
found in the tertiary structure
Disulfide bridges can be of two types:
Intrachain
Interchains
The one polypeptide chain in
oligomeric protein is called : ………..
Oligomeric protiens
All subunits should be different
True
False
Oligomeric protiens
4 chains Heamoglobin
2 alpha and 2 beta
chians
Oligomeric protiens
On the otherhand, some proteins
such as LDH enzyme is
composed of 4 identical subunits.
The final folded protein shape
Determines the final function
of this protien
Protein folding
There are 2 main final shapes of folded proteins:
Globular proteins
fibrous proteins
Globular proteins
Spherical in their final shape
Water soluble
Contains mixture of α β and other
random structures
Enzymes, transport proteins, hormones
and antibodies
fibrous proteins
Are structural protiens
Water insoluble
Built of either α or β
Include cellulose fiber in the cell wall of plant
cells
Collagen and elastin in human
Keratin in the hair and nails
Chitin in the cuticle of some organisms
What you need to know to
investigate the protein structure
I- Molecular mass determination :
1- SDS-PAGE
2- Exclusion chromatography
Size exclusion chromatography