Acid Key: A
= alanine C = cysteine D
= aspartic acid I = isoleucine
G = glycine K = lysine L
= leucine N
= asparagine P = proline
Q = glutamine R
= arginine S = serine T
= threonine V = valine Y
Note that the LQQA
sequence is common to both proteins. When the entire sequence
of these two proteins is considered, there is about 40% overlap
of identical sequences.
|Amino acids that
have no electric charge avoid water and are attracted to lipid
and each other. As a result, they form a
coil. So, to simplify the representation of those
sections of a protein, they are shown as a coiled ribbon
(see diagram on right).
below represents the combined result of coiling and folding of a
protein when it gets embedded in a membrane.
This picture shows two
ways of drawing a membrane protein.
Left: secondary coiled structure, with
the coiled part buried in the membrane. The small letters are
the first letter of names of the amino acids, showing the
sequence as we explained at the top of this page.
Middle: a "ribbon" diagram" of
the same thing, with the red parts representing uncoiled amino
acid strands that are outside of the membrane.
Far right: diagrams showing how the structure might
look if you were looking down on the membrane rather than looking
at it from the side. Photograph courtesy of Dr. Fillipp Oesterhelt,
University of Munich, Germany.