Relationship of zipper groups to the ten homosteric zipper classes, eight of which have previously been described (Sawaya et al., 2007). Zipper groups are organized by the rotation and translation components of the generators. Zipper groups that satisfy previously identified homosteric zipper classes are labeled in red. Zipper groups that do not satisfy any of the previously identified classes are labeled in blue. E (identity) and the generators in the row and column headings produce the zipper groups listed in each cell of the chart (see also Table 2). Not shown here is zipper group 1b (shown in Fig. 1i), which is generated by E and Jxy. Zipper groups that satisfy the same homosteric zipper classes are shown connected by a line or boxed together.