Figure 1. I/L core packing in the Hv Coiled coil domain.

A, sequence alignment of the C-terminal cytoplasmic Coiled coil domain from various species of Hv. Coiled-coil residues occupying hydrophobic ‘a’ and ‘d’ positions are denoted by blue and red, respectively. Layer positions for each residue in the structure are indicated below the alignment. The green box depicts part of S4. B, hydrophobic layers of the coiled-coil core. Van der Waals spheres depicting the side chains of the ‘a’ (red) and ‘d’ (blue) layers on a ribbon backbone (grey) are shown. Layer numbers, amino acid residues and the N- and C-termini of the coiled coil are indicated. C, representative geometry of the symmetrically packed hydrophobic I/L type coiled-coil core. Highlighted in the hydrophobic core are two Ile residues in layer 9 (red) and two Leu residues in layer 10 (blue). Ball-and-stick representations show each layer of the core. ‘a’ and ‘d’ positions are coloured as in (A). D, helical wheel representation of the core-packing arrangements found in the homodimeric coiled coil. Heptad repeat positions are labelled a–g. Core-forming positions are highlighted in colour as in (A), and positions lying in the same layer are linked by solid or dashed lines.