The Protein Data Bank (PDB) at Brookhaven National Laboratory, is a database containing experimentally determined three-dimensional structures of proteins, nucleic acids and other biological macromolecules, with approximately 8000 entries. Data are easily submitted via PDB's WWW-based tool AutoDep, in either mmCIF or PDB format, and are most conveniently examined via PDB's WWW-based tool 3DB Browser.
Sussman, J. L., Lin, D., Jiang, J., Manning, N. O., Prilusky, J., Ritter, O., & Abola, E. E. (1998). Protein Data Bank (PDB): Database of three-dimensional structural information of biological macromolecules. In Acta Crystallographica Section D: Biological Crystallography (Vol. 54, pp. 1078–1084). https://doi.org/10.1107/S0907444998009378