Biology Reference
In-Depth Information
A
B
F
IGURE
6. The principle of self-assembly.
In order to create unique structures,
proteins must interact unequivocally.
A
: Example of a single protein that self-
assembles to form a viral or cell structure. AD, BE and CF are the only contacts
possible.
B
: Example of an icosahedral viral structure. The protein is symbolised
by an irregular polygon. No polygon can interact other than through an identical
side of another polygon. If these rules were not respected, ontogenesis would not
be possible because it would end in multiple structures formed at the whim of
molecular encounters. We are grateful to Donald Caspar, Aaron Klug and CSH
Press for permission to reproduce this figure (Caspar and Klug, 1962).
the polygons. If the molecules could also be bound by their other
sites, a combination of possible interactions would be created and
the spontaneous self-assembly of these molecules would no longer
produce a unique viral structure. Several forms would be possible,
each with a probability of being produced which would depend on
the combination possibilities and the frequency of interactions
between the molecules.
