Greetings,
Currently working on a DNA quadruplex structure in which 4 of the 10
residues are partially disordered. 1.50 A resolution, and currently
refined to R/Rfree of 12/14%. Apparent spacegroup is P4, two molecules
in AU, both of which reside on the 4-fold to generate quadruplexes.
Packing results in layers of quadruplexes that are perpendicular to the
4-fold. The issue is with the diordered residues that appear to mediate
crystal contacts between these layers. There are some difference density
planes that runs between the layers, and they are spaced 3.2 A apart,
which would suggest nucleobase stacking, but there is no way to build
into it.
Are there other examples of disordered (or most disordered) residues
mediating crystal contacts in this way? I seem to recall some examples
with partially disordered protein subunits/monomers being involved in
packing. Other things to consider?
Thanks,
--paul
