Unique stabilizing interactions identified in the two‐stranded α‐helical coiled‐coil: Crystal structure of a cortexillin I/GCN4 hybrid coiled‐coil peptide

Abstract

We determined the 1.17 Å resolution X-ray crystal structure of a hybrid peptide based on sequences from coiled-coil regions of the proteins GCN4 and cortexillin I. The peptide forms a parallel homodimeric coiled-coil, with C ␣ backbone geometry similar to GCN4 (rmsd value 0.71 Å). Three stabilizing interactions have been identified: a unique hydrogen bonding-electrostatic network not previously observed in coiledcoils, and two other hydrophobic interactions involving leucine residues at positions e and g from both g-a and d-e interchain interactions with the hydrophobic core. This is also the first report of the quantitative significance of these interactions. The GCN4/cortexillin hybrid surprisingly has two interchain Glu-LysЈ ion pairs that form a hydrogen bonding network with the Asn residues in the core. This network, which was not observed for the reversed Lys-GluЈ pair in GCN4, increases the combined stability contribution of each Glu-LysЈ salt bridge across the central Asn15-Asn15Ј core to ∼0.7 kcal/mole, compared to ∼0.4 kcal mole −1 from a Glu-LysЈ salt bridge on its own. In addition to electrostatic and hydrogen bonding stabilization of the coiled-coil, individual leucine residues at positions e and g in the hybrid peptide also contribute to stability by 0.7 kcal/mole relative to alanine. These interactions are of critical importance to understanding the stability requirements for coiled-coil folding and in modulating the stability of de novo designed macromolecules containing this motif.

A New Mechanism for Metal Ion-assisted Interchain Helix Assembly in a Naturally Occurring Peptide Mediated by Optimally Spaced γ-Carboxyglutamic Acid Residues

“…In frequent examples of coiled-coil structures, residues at positions e and g 0 (parallel coiled-coils) or positions g and g 0 , and e and e 0 (antiparallel coiled-coils) interact ( Figure 10). In the case of parallel strands, when e and g 0 are hydrophobic, dimeric coiledcoils are favored, and when these residues are oppositely charged, and can associate via chargecharge interactions, as is the case in the majority of coiled-coils, 31 higher-order oligimerization states are favored. 25 Interchain electrostatic interactions (attractions versus repulsions) between e and g 0 and e 0 and g, as well as the specific nature of these residues, not only stabilize coiled-coil interactions, but also control the orientation of the helical strands, e.g.…”

Charged Amino Acids of the N-terminal Domain Are Involved in Coupling Binding and Gating in α7 Nicotinic Receptors

“…A wide network of interactions would then be possible as polar and charged residues not only have pairwise interactions in proteins but also form structurally and functionally relevant networks able to link distant domains in proteins (23,24). Different residues, including Glu-45, Lys-46, Asp-128, and Asp-135, would participate in this network although with diverse requirements and roles.…”

Vimentin Coil 1A—A Molecular Switch Involved in the Initiation of Filament Elongation

“…In the case of E103, its negative charge is compensating the helix dipole and so should not be changed. While asparagine contributes least to coiled-coil stability [ΔΔG u (Ala) = 0.9] 34 , its ability to form hydrogen bonds with the other chain may be important to determine the specific oligomerisation state of the coiled coil; 36,37 for this reason, we did not modify this residue.…”