Its purpose was to provide the proteomics community with a resource that enables In its last version, the IPI contained the complete reference sets for six animal species: Homo sapiens (human), Mus musculus (mouse), Rattus norvegicus (rat), Bos taurus (cattle), Gallus gallus (chicken) and Danio rerio (zebrafish); and one plant species: Arabidopsis thaliana (thale cress).
The human, mouse and rat datasets were the first to be developed, combining information taken from the Swiss-Prot, TrEMBL, Ensembl and RefSeq databases.
[1] In 2001, when the IPI was launched, databases cataloguing human genes varied greatly and had few links between them.
Currently many model organisms have a reference set of genes/proteins which are catalogued in Ensembl/UniProt respectively, as well as other species specific databases.
EBI advised users of its services to employ UniProtKB accession numbers as their protein identifiers.