Rational Design of Helical Nanotubes from Self-Assembly of Coiled-Coil Lock Washers

Design
of a structurally defined helical assembly is described
that involves recoding of the amino acid sequence of peptide GCN4-pAA. In solution and the crystalline state, GCN4-pAA adopts a 7-helix bundle structure that resembles a supramolecular
lock washer. Structurally informed mutagenesis of the sequence of GCN4-pAA afforded peptide 7HSAP1, which undergoes
self-association into a nanotube via noncovalent interactions between
complementary interfaces of the coiled-coil lock-washer structures.
Biophysical measurements conducted in solution and the solid state
over multiple length scales of structural hierarchy are consistent
with self-assembly of nanotube structures derived from 7-helix bundle
subunits. The dimensions of the supramolecular assemblies are similar
to those observed in the crystal structure of GCN4-pAA. Fluorescence studies of the interaction of 7HSAP1 with
the solvatochromic fluorophore PRODAN indicated that the nanotubes
could encapsulate shape-appropriate small molecules with high binding
affinity.