CATH Get Domain Summary

Get CATH structural classification for a specific protein domain from PDB. Domains are identified by PDB code + chain + domain number (e.g., 1cukA01). Returns the full CATH hierarchy (Class, Architecture, Topology, Homologous superfamily) and residue count. Example: '1cukA01' returns CATH ID 2.40.50.140.116.1.1.1.1 (Mainly Beta class, Nucleic acid-binding proteins superfamily) with 212 residues.