Protein structure is
very complex because the different amino acids cause coiling
and folding in different ways. We should think about protein
structure in two ways:
simple two-dimensional chains of amino acids.
structure: chains that are coiled.
coiled chains that are folded.
One way to get the idea is to cut a sheet of paper in half,
lengthwise. Mark a couple of colored spots on it, to
represent "hot spots" or active regions of the
Now crumple the paper up in different ways.
paper represents amino acids laid out lengthwise. Red spots
represent small regions of amino acid "hot spots" that can attract and bind things like drugs or hormones.
Depending on how the
paper folds, the hot spots are in different positions. Looking
at the picture on the left, a drug or hormone that needs to bind
to two hot spots
has to have a compatible shape that can bind. But that same
drug could not bind if the protein were folded as on the right.
When clusters of
different proteins clump together as sub-units of a much larger
glob, this creates was is called quaternary structure.
For a more
complete illustration of the four levels of structure, click
here. (This website contains some good illustrations of the
levels of protein structure.)
parts of a protein may be strongly bonded because of atomic
bridges that link two regions. Sulphur-sulphur bonds commonly
create such bridges in proteins. (These are the same bridges
that get broken and reformed during a hair perm. They're what
causes part of the hair perm smell too.)
Certain toxins damage
cells because they impose extra bridges that do not normally
occur (see our discussion of the hazards of hexane).
stands for a different amino acid)
(structure is now coiled, similar to a spring
(folds back and forth on itself, similar to a piece of string
that has been twisted too much.)
(several protein units form a big glob)