02134nas a2200241   4500008004100000245005900041210005800100300001100158490000700169520128500176653008301461653003201544653003201576653005801608100001601666700001301682700002401695700001401719700001901733700001901752700001501771856010601786       2001                        eng d00aClassification of protein disulphide-bridge topologies0 aClassification of protein disulphidebridge topologies  a477-870 v153 aThe preferential occurrence of certain disulphide-bridge topologies in proteins has prompted us to design a method and a program, KNOT-MATCH, for their classification. The program has been applied to a database of proteins with less than 65% homology and more than two disulphide bridges. We have investigated whether there are topological preferences that can be used to group proteins and if these can be applied to gain insight into the structural or functional relationships among them. The classification has been performed by Density Search and Hierarchical Clustering Techniques, yielding thirteen main protein classes from the superimposition and clustering process. It is noteworthy that besides the disulphide bridges, regular secondary structures and loops frequently become correctly aligned. Although the lack of significant sequence similarity among some clustered proteins precludes the easy establishment of evolutionary relationships, the program permits us to find out important structural or functional residues upon the superimposition of two protein structures apparently unrelated. The derived classification can be very useful for finding relationships among proteins which would escape detection by current sequence or topology-based analytical algorithms.10aAlgorithms Computer Simulation Databases as Topic Disulfides/*chemistry Models10aMolecular Protein Structure10aSecondary Protein Structure10aTertiary Proteins/*chemistry/*classification Software1 aMas, J., M.1 aAloy, P.1 aMarti-Renom, M., A.1 aOliva, B.1 ade Llorens, R.1 aAviles, F., X.1 aQuerol, E.  uhttp://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=11394740