quaternary structures. UniParc UniProt Archive (UniParc) is a comprehensive and non-redundant database, which contains all the protein sequences from the main, publicly available protein sequence databases. Proteins may exist in several different source databases, and in multiple copies in the same database. In order to avoid redundancy, UniParc stores each unique sequence only once. Identical sequences are merged, regardless of whether they are from the same or different species. Each sequence is given a stable and unique identifier (UPI), making it possible to identify the same protein from different source databases. UniParc contains only protein sequences, with no annotation. Database cross-references in UniParc entries allow further information about the protein to be retrieved from the source databases. When sequences in the source databases change, these changes are tracked by UniParc and history of all changes is archived. Source databases Currently UniParc contains protein sequences from the following publicly available databases: INSDC EMBL-Bank/DDBJ/GenBank nucleotide sequence databases Ensembl European Patent Office (EPO) FlyBase: the primary repository of genetic and molecular data for the insect family Drosophilidae (FlyBase) H-Invitational Database (H-Inv) International Protein Index (IPI) Japan Patent Office (JPO) Protein Information Resource (PIR-PSD) Protein Data Bank (PDB) Protein Research Foundation (PRF) RefSeq Saccharomyces Genome Database (SGD) The Arabidopsis Information Resource (TAIR) TROME US Patent Office (USPTO) UniProtKB/Swiss-Prot, UniProtKB/Swiss-Prot protein isoforms, UniProtKB/TrEMBL Vertebrate and Genome Annotation Database (VEGA) WormBase UniRef The UniProt Reference Clusters (UniRef) consist of three databases of clustered sets of protein sequences from UniProtKB and selected UniParc records. The UniRef100 database combines identical sequences and sequence fragments (from any organism) into a single UniRef entry. The sequence of a representative protein, the accession numbers of all the merged entries and links to the corresponding UniProtKB and UniParc records are displayed. UniRef100 sequences are clustered using the CD-HIT algorithm to build UniRef90 and UniRef50. Each cluster is composed of sequences that have at least 90% or 50% sequence identity, respectively, to the longest sequence. Clustering sequences significantly reduces database size, enabling faster sequence searches. UniRef is available from the UniProt FTP site. Funding UniProt is funded by grants from the National Human Genome Research Institute, the National Institutes of Health (NIH), the European Commission, the Swiss Federal Government through the Federal Office of Education and Science, NCI-caBIG, and the US Department of Defense. References External links UniProt Biological databases Online databases Proteomics Science and technology in Cambridgeshire South Cambridgeshire District Bioinformatics Computational