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4BICH001W Biochemistry
Amino Acids & Protein Function
Amino Acids and Proteins
Learning outcomes:
1
...
2
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3
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4
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Amino acids have a general structure of two carbon atoms,
one of which is part of a carboxylic acid group, while the
other has an amine group - Amino Acids
...
Mathews, van
Holde, and Ahern
Biochemistry 3rd edition
...
Mathews, van
Holde, and Ahern
Biochemistry 3rd
Levels of protein
structure…
Figs
...
1
...
In organic chemistry, this would be called an amide
...
Mathews, van Holde, and Ahern Biochemistry 3rd edition
...
Mathews, van
Holde, and Ahern
Biochemistry 3rd
edition
...
The location of these bonds is regarded as part of the primary
structure - but they can have an important influence on tertiary
structure…
Figs
...
e
...
Lysozyme –
structure
stabilised by 4
disulphide bonds…
http://users
...
com/jkimball
...
ultranet/BiologyPages/L/Lysozy
me
...
Mathews, van Holde,
and Ahern Biochemistry 3rd
edition
...
Proteins do NOT simply consist of a randomly coiled chain of
amino acids – they usually have a very well defined structure
...
Secondary structure
Associations between amino acids (particularly hydrogen bonds
between the C=O and N-H of different peptide bonds) can lead
to formation of a number of simple and stable repetitive
conformations
...
In an -helix, the peptide chain is coiled so that hydrogen
bonds are formed between the C=O of the peptide group of
one amino acid and the N-H of the peptide group of another
amino acid four ahead in the primary structure
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4 A / 360o
3
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mit
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html
C
N
From Biochemistry 2nd Ed
...
mit
...
html
It is common to show -sheets as broad arrows…
Human Retinol (in blue) binding protein
Sucrose membrane transporter protein
from Salmonella typhimurium
Sucrose
Retinol
Segments of the amino acid sequence that do not form defined
secondary structures are usually called loops and are found
on the surface of proteins…
loop
Fructosamine-3-kinase from H
...
Tertiary Structure
The folding of a protein in three dimensions is referred to as
tertiary structure
...
These include:
• Hydrogen bonding (e
...
Asn (N), Gln (Q), Ser (S), Thr (T))
• Hydrophobic interactions (e
...
Ile (I), Leu (L), Val (V))
• Electrostatic interactions (e
...
Arg (R), Asp (D), Glu (E), Lys (K))
Chymotrypsin (a serine proteinase)
Chymotrypsin is digestive enzyme that can break (i
...
hydrolyse)
peptide bonds in proteins…
Peptide bond
What is the link between structure
and function?
Structural alignment chymotrypsin, trypsin, and elastase:
D102, H57 & S195 make up
the key active site residues
that allow the serine proteinase
to hydrolyse the peptide bond
...
His-57 (H57), Asp-120 (D120) & Ser-195 (S195)
form catalytic triad required for activity…
www
...
com/mathews/ch09/frames
...
wikipedia
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wikipedia
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soton
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uk/~jbc2/folding