Fig. 1.

Pairwise and cyclically complementary knobs-into-holes interactions. (A) A view into the interface of a parallel, dimeric coiled coil. The central line of four residues represents a layer. Side chains are contributed from both helices: Those in white are from the furthermost helix shown as a ribbon, and thus, point toward the viewer; those shaded grey are from the near helix and point into the paper. Dotted lines link the centers of mass of the side chains, which are indicated by black circles. (B) A schematic representation of part A using the same shading and highlighting the knob (k) and hole (h) residues. (C) A layer of cyclically complementary knobs-into-holes interactions in a trimeric coiled coil. The view is from above the layer (i.e., down the superhelical axis). Each strand is shaded differently. The leucine residues are the knobs and the bases of the holes are highlighted by straight lines. The ribbon diagrams shown here and in subsequent figures were created using molscript (Kraulis 1991).