Helical coiled-coils and bundles are some of the
most common structural motifs found in proteins. Design
and synthesis of α-helical motifs may provide interesting
scaffolds that can be useful as host structures to display
functional sites, thus allowing the engineering of novel
functional miniproteins. We have synthesized a 38-amino
acid peptide, α2p8, encompassing the α-helical
hairpin present in the structure of p8MTCP1,
as an α-helical scaffold particularly promising for
its stability and permissiveness of sequence mutations.
The three-dimensional structure of this peptide has been
solved using homonuclear two-dimensional NMR techniques
at 600 MHz. After sequence specific assignment, a total
of 285 distance and 29 dihedral restraints were collected.
The solution structure of α2p8 is presented
as a set of 30 DIANA structures, further refined by restrained
molecular dynamics, using simulated annealing protocol
with the AMBER force field. The RMSD values for the backbone
and all heavy atoms are 0.65 ± 0.25 and 1.51 ±
0.21 Å, respectively. Excised from its protein context,
the α-hairpin keeps its native structure: an α-helical
coiled-coil, similar to that found in superhelical structures,
with two helices spanning residues 4–16 and 25–36,
and linked by a short loop. This motif is stabilized by
two interhelical disulfide bridges and several hydrophobic
interactions at the helix interface, leaving most of its
solvent-exposed surface available for mutation. This α-helical
hairpin, easily amenable to synthetic chemistry and biological
expression system, may represent a stable and versatile
scaffold to display new functional sites and peptide libraries.