UniProt release 5.1

Average of more than 10 cross-references per UniProtKB/Swiss-Prot entry

As described in the UniProt Knowledgebase user manual, integration with other data resources is one of the priorities of UniProtKB/Swiss-Prot.

This is reflected in the high number of cross-references: UniProtKB/Swiss-Prot currently contains more than 1.8 million explicit cross-references, which translates to just over 10 links per Swiss-Prot entry. 68 external databases are referenced in this manner, in addition to the 32 databases to which we link via implicit links, created on the fly by the ExPASy server. All these resources are listed in the List of databases cross-referenced in Swiss-Prot.

The most represented type of cross-references are the ones to the family and domain classification databases, i.e. InterPro and its member databases, as well as, obviously, the nucleotide sequence database (DR EMBL), our main source for sequence data.