Families of Structurally Similar Proteins or FSSP is a database of structurally superimposed proteins generated using the "Distance-matrix ALIgnment" (DALI) algorithm.The database currently contains an extended structural family for each of 330 representative protein chains.
Very close homologs (above 70% sequence identity) are excluded as they rarely have marked structural differences.
The alignments of remote homologs are the result of pairwise all-against-all structural comparisons in the set of 330 representative protein chains.
The significance of structural similarity is estimated based on statistical criteria.
[1] The database is helpful for the comparison of protein structures.