| Table 2.Comparison of coiled-coil types
| |||
| Ferritin-type Alacoil | ROP-type Alacoil | Classic coiled-coil | |
| Helix directions | Antiparallel | Antiparallel | Parallel |
| Helix-axis spacing | 7.5 A | 8.5 A | 9.6 A |
| Fraction offset/heptad | 0.2-0.25(offset) | 0.4-0.5("aligned")* | 0(aligned) |
| Main contact site | Ala in "a" | Ala in "d" | Leu in "d" |
| Contact layer(s) | Layers same:a-d | Layers same: d-a | Layers same: d-d, a-a |
| Contact side(s) | Sides different: tip versus knuckle | Sides different: tip versus knuckle | Sides same |
| Hole opposite knob | Triangle up: i-3, i, i+1 | Triangle down: i,i+1, i+4 | Diamond: i-3, i, i+1, i+4 |
| Occurrence as long coil | in five unrelated globular or membrane proteins | In two unrelated globular proteins | Leu zip dimers;fibrous proteins |
*Detailed parameters for the classic coiled-coil are taken from the GCN4 leucine zipper structure *Helix turns are aligned, although two-turn heptad repeat is offset by 0.5 The Menu The Introduction | |||