GenBank, EMBL and DDBJ also maintain protein sequences.

UniProt (Universal Protein Resource) [UniProt Consortium 2007] is the world's most comprehensive catalog of information on proteins. It is a central repository of protein sequence and function created by joining the information contained in Swiss-Prot, TrEMBL, and PIR. UniProt is comprised of three components, each optimized for different uses. The UniProt Knowledgebase (UniProt) is the central access point for extensive curated protein information, including function, classification, and cross-reference. The UniProt Non-redundant Reference (UniRef) databases combine closely related sequences into a single record to speed searches. The UniProt Archive (UniParc) is a comprehensive repository, reflecting the history of all protein sequences.

InterPro [Mulder et al. 2007] is a database of protein families, domains and functional sites in which identifiable features found in known proteins can be applied to unknown protein sequences.

ENZYME [Bairoch 2000] is a repository of information relative to the nomenclature of enzymes. It is primarily based on the recommendations of the Nomenclature Committee of the International Union of Biochemistry and Molecular Biology (IUBMB) and it describes each type of characterized enzyme for which an EC (Enzyme Commission) number has been provided.

SWISS-2DPAGE [Hoogland et al. 2004] contains data on proteins identified on various 2-D PAGE and SDS-PAGE reference maps. You can locate these proteins on the 2-D PAGE maps or display the region of a 2-D PAGE map where one might expect to find a protein from Swiss-Prot.

The Protein Data Bank (PDB) [Berman et al. 2007] is the single worldwide repository for the processing and distribution of 3-D structure data of large molecules of proteins and nucleic acids.