1. CATH – a hierarchic classification of protein domain structures Rui Kuang

2. CATH Hierarchy Class: secondary structure composition and contacts mainly alpha, mainly beta and alpha-beta Architecture: description of the gross arrangement of secondary structures, independent of connectivity Structures with diverse connectivities but common architecture, such as barrel, sandwich and roll

3. CATH Hierarchy Topology: fold families similar number and arrangement of secondary structures with the same connectivity links Homologous superfamily: highly similar structures and functional similarity Sequence family: significant sequence similarity and thus a high probability of having similar structure/function

4. Example:

5. Class into Architecture In alpha protein only four-helix bundle architecture is distinguishable. More appropriate to group reflecting combinations of common motifs The constrains on beta strands to be hydrogen bonded within sheets and sheet- sheet packing make them distinct Alpha-beta class are more constrained and only has eight architectures.

6. Procedures of building CATH