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Similar to 03 proteins (20)
03 proteins
- 2. PRIMARY STRUCTURE
The sequence of amino acids
MIL1 sequence:
>gi|7662506|ref|NP_056182.1| MIL1 protein [Homo sapiens]
MEDCLAHLGEKVSQELKEPLHKALQMLLSQPVTYQAFRECTLETTVHASGWNKILVPLVLLRQMLL
ELTRLGQEPLSALLQFGVTYLEDYSAEYIIQQGGWGTVFSLESEEEEYPGITAEDSNDIYILPSDN
SGQVSPPESPTVTTSWQSESLPVSLSASQSWHTESLPVSLGPESWQQIAMDPEEVKSLDSNGAGEK
SENNSSNSDIVHVEKEEVPEGMEEAAVASVVLPARELQEALPEAPAPLLPHITATSLLGTREPDTE
VITVEKSSPATSLFVELDEEEVKAATTEPTEVEEVVPALEPTETLLSEKEINAREESLVEELSPAS
EKKPVPPSEGKSRLSPAGEMKPMPLSEGKSILLFGGAAAVAILAVAIGVALALRKK
length: 386amino acids © Anne-Marie Ternes
- 3. PRIMARY STRUCTURE
The numbers of amino acids vary
(e.g. insulin 51, lysozyme 129, haemoglobin
574, gamma globulin 1250)
The primary structure determines the folding of
the polypeptide to give a functional protein
Polar amino acids (acidic, basic and neutral)
are hydrophilic and tend to be placed on the
outside of the protein.
Non-polar (hydrophobic) amino acids tend to be
placed on the inside of the protein
© 2007 Paul Billiet ODWS
- 4. Infinite variety
The number of possible sequences is
infinite
An average protein has 300 amino acids,
At each position there could be one of 20
different amino acids
= 10390
possible combinations
Most are useless
Natural selection picks out the best
© 2007 Paul Billiet ODWS
- 5. SECONDARY STRUCTURE
The folding of the N-C-
C backbone of the
polypeptide chain
using weak hydrogen
bonds
© Science Student
© Text 2007 Paul Billiet ODWS
- 6. SECONDARY STRUCTURE
This produces the alpha helix and beta pleating
The length of the helix or pleat is determined by certain
amino acids that will not participate in these structures
(e.g. proline)
© Dr Gary Kaiser
© Text2007 Paul Billiet ODWS
- 7. TERTIARY STRUCTURE
The folding of the polypeptide into
domains whose chemical properties are
determined by the amino acids in the
chain
MIL1 protein
© Anne-Marie Ternes
© 2007 Paul Billiet ODWS
- 8. TERTIARY STRUCTURE
This folding is sometimes held together by
strong covalent bonds
(e.g. cysteine-cysteine disulphide bridge)
Bending of the chain takes place at certain
amino acids
(e.g. proline)
Hydrophobic amino acids tend to arrange
themselves inside the molecule
Hydrophilic amino acids arrange themselves
on the outside
© 2007 Paul Billiet ODWS
- 9. © Max Planck Institute for Molecular Genetics
Chain B of Protein Kinase C
- 10. QUATERNARY STRUCTURE
Some proteins are
made of several
polypeptide subunits
(e.g. haemoglobin has
four)
Protein Kinase C
© Max Planck Institute for Molecular Genetics
© Text 2007 Paul Billiet ODWS
- 11. QUATERNARY STRUCTURE
These subunits fit together to form the
functional protein
Therefore, the sequence of the amino
acids in the primary structure will influence
the protein's structure at two, three or
more levels
© 2007 Paul Billiet ODWS
- 13. PROTEIN FUNCTIONS
Protein structure determines protein
function
Denaturation or inhibition which may
change protein structure will change its
function
Coenzymes and cofactors in general may
enhance the protein's structure
© 2007 Paul Billiet ODWS
- 14. Fibrous proteins
Involved in structure: tendons ligaments
blood clots
(e.g. collagen and keratin)
Contractile proteins in movement: muscle,
microtubules
(cytoskelton, mitotic spindle, cilia, flagella)
© 2007 Paul Billiet ODWS
- 15. Globular proteins
most proteins which move around (e.g.
albumen, casein in milk)
Proteins with binding sites:
enzymes, haemoglobin, immunoglobulins,
membrane receptor sites
© 2007 Paul Billiet ODWS
- 16. Proteins classified by function
CATALYTIC: enzymes
STORAGE: ovalbumen (in eggs), casein (in milk), zein
(in maize)
TRANSPORT: haemoglobin
COMMUNICATION: hormones (eg insulin) and
neurotransmitters
CONTRACTILE: actin, myosin, dynein (in microtubules)
PROTECTIVE: Immunoglobulin, fibrinogen, blood
clotting factors
TOXINS: snake venom
STRUCTURAL: cell membrane proteins, keratin (hair),
collagen
© 2007 Paul Billiet ODWS