Secondary protein structures
Alpha helices & Beta pleated sheets
The alpha
helix
and beta
pleated
sheet forms are alternative configurations of the N - C(R) - C backbone
residues. The alpha helix
is a right-handed helix,
from which the radical (R)
groups are directed outward at right angles. The helix is
stabilized by
H-bonds between non-adjacent residues. The beta sheet consists of a
series of
molecules
running anti-parallel to each other. The
radical (R) groups
are directed
outward at right-angles, alternatively above and below the
plane of the
sheet: the sheet is stabilized by H-bonds between carboxy
and amino
groups of adjacent antiparallel molecules.
These regular structures are a consequence of the
exclusively L forms of the
amino acids.
Figure © 2012 TA Brown, Introduction
to Genetics (1st ed.); additional
text © 2014 by Steven M. Carr