The Babraham Institute. The links are designed to take the user directly to the sequence in question, rather than presenting menus.
Links work at family, enzyme and sequence levels.
Prof. J.M. Thornton at University College, London. This is also a classification of protein domains, and high resolution tertiary structures are a requirement. Proteins are classified into superfamilies, topologies, architectures and classes. HSSP HSSP is a collection of alignments. The alignments are based on comparisons of tertiary structures, so only those families for which a tertiary structure has been resolved are included.