scop

SCOP stands for Structural Classification of Proteins. It is a manually curated database that provides a hierarchical classification of protein structural domains based on similarities in structure and evolutionary relationships. The project was initiated by Alex S. Murzin, Stephen E. Brenner, Timothy L. Hubbard, and Cyrus A. Orengo and first released in 1995. SCOP organizes protein domains into four levels: Class, Fold, Superfamily, and Family. Each domain is associated with a representative structural entry from the Protein Data Bank (PDB) and linked to available functional annotations and literature when possible. The overarching aim is to reflect both structural similarity and evolutionary relationships to aid functional inference and the identification of distant homologues.

SCOP emphasizes expert, manual curation in addition to structural data, using established criteria to group domains that share common ancestry or similar folds. The database has been widely used for benchmarking protein fold recognition methods, for exploring protein evolution, and for identifying structural relationships across diverse protein families.

Since its original release, SCOP has been complemented by SCOPe (Structural Classification of Proteins—extended), which adds automatic assignment of new structures while preserving curation standards, and SCOP2, a redesigned framework that updates classification criteria and supports a more flexible schema to accommodate growing structural data and evolving understanding of protein evolution. These extensions strive to keep pace with advances in structural biology and enable broader, up-to-date analyses of the protein structure universe.