Architecture groups domains with similar secondary structure compositions and geometric shapes.


X-group groups domains that are possible homologs with some yet inadequate evidence to support the homology relationships. In practice, they frequently share structural similarity.


H-group groups domains that we think are homologous based on various consideration, such as high sequence or structure scores, functional similarity, unusual features and literature.


T-group groups domains with similar topological connections. Homologs with distinct topologies are separated in different T-groups under the same H-group.


F-group groups domains with significant sequence similarity in a family. Currently, F-groups consist of a large proportion of mapped Pfam families and some HHsearch-based clusters.

Provisional representative

An automatically assigned domain is designated as a provisional representative when the F-group does not contain any manual representative.