Binding sites on nucleic acids
have three kinds of asymmetry and symmetry: asymmetric - All sites on RNA and
probably most if not all sites on DNA bound by a single polypeptide will be
asymmetric. Example: RNA: splice sites; DNA: T7 RNA polymerase binding sites. Symmetric - Sites on DNA bound by a
usually (there are exceptions!) Have a two-fold dyad axis of symmetry. This
means that there is a line passing through the DNA, perpendicular to its long
axis, about which a 180 degree rotation will bring the DNA helix phosphates
back into register
with their original positions. There are two places that the dyad axis can be
set: odd symmetric - The axis is on a single base, so
that the site contains an odd number of bases.
of 8 logos: lambda ci and cro and Lambda O. Even symmetric - The axis is
between two bases,
so that the site contains an even number of bases.
of 8 logos: 434 ci and cro, argr, CRP, trpr, FNR, lexa.