This represents 15% of Pfam families and as these tend to represent the larger protein families, account for 31% of the domain hits in Pfam. Clans help us to improve the annotation of families. For example, knowing the 3D structure of a domain is an essential part of understanding the biology of that domain.Pfam clans are helping to identify, previously undetected, structural homologues. Currently, 66% of all families in clans contain at least one sequence with a known 3D structure.his represents 15% of Pfam families and as these tend to represent the larger protein families, account for 31% of the domain hits in Pfam. Clans help us to improve the annotation of families. For example, knowing the 3D structure of a domain is an essential part of understanding the biology of that domain.