Table 2. The 19 possible combinations of generators produce 15 distinct zipper groups.
Zipper-group names are based on the homosteric zipper classes described previously (Sawaya et al., 2007 ▶). Underlined positions are group generators. Each homosteric zipper class corresponds to two distinct zipper groups except for homosteric zipper classes 2, 3, 4, 8 and 9. The penultimate column indicates alternate symmetry that arises from the shift of one -sheet relative to the other along the z axis (described in the text). The last column indicates whether the symmetry of the zipper group requires the -sheets to be eclipsed, where neighboring -strands in the two -sheets are in the same plane.
| Zipper group | Positions | Layer group | Principal axis | Alternate symmetry | Eclipsed |
|---|---|---|---|---|---|
| 2 | E | 1 (p111) | N | ||
| 4 | E, Ix | 9 (p2111) | x (21) | N | |
| 6a | E, Iy | 8 (p211) | x (twofold) | p2111 | Y |
| 4 | E, Ixy | 9 (p2111) | x (21) | N | |
| 1a | E, Jx | 8 (p121) | y (twofold) | Y | |
| 7a | E, Jy | 9 (p1211) | y (21) | N | |
| 1b | E, Jxy | 9 (p1211) | y (21) | N | |
| 3 | E, Kx | 3 (p112) | z (twofold) | p1121 | N |
| 9 | E, Ky | 3 (p112) | z (twofold) | c112 | N |
| 3 | E, Kxy | 3 (p112) | z (twofold) | p1121 | N |
| 6b | E, Ix, Iy, xy | 10 (c211) | x (21 and twofold) | p2111 | Y |
| 8 | E, Ix, Jy, Kxy | 21 (p21212) | p212121 | N | |
| 10a | E, Ix, Ky, Jxy | 21 (p21212) | N | ||
| 5a | E, Jx, Iy, Kxy | 19 (p222) | p121 | Y | |
| 7b | E, Jx, Jy, xy | 10 (c121) | y (21 and twofold) | Y | |
| 10b | E, Jx, Ky, Ixy | 20 (p2122) | Y | ||
| 5b | E, Kx, Iy, Jxy | 20 (p2212) | p1211 | Y | |
| 8 | E, Kx, Jy, Ixy | 21 (p21212) | p212121 | N | |
| 9 | E, Kx, Ky, xy | 3 (b112) | z (twofold) | i112 | N |