Figure 1.

Crick parameterization of parallel and antiparallel coiled coils. (a-b) Schematic illustrating parameters used to describe (a) parallel and (b) antiparallel backbone geometries. For each wheel diagram, the heptad positions are indicated in lowercase letters and the direction of the chain is indicated by whether the N or C terminus is out of the page. For the structural diagram, the a and a’ positions are shown in black, the d and d’ positions in gray, and the rest in white. (c) Distribution of the backbone RMSD (N, Cα, and C atoms) for the native crystal structures in the test set to the closest ideal structure in the backbone sets. For every example, an idealized model with an RMSD of less than 1.8 Å was available for selection as a template.