UniParc is the main sequence storehouse and is a comprehensive repository that reflects the history of all protein sequences (1). UniParc contains all new and revised protein sequences from all publicly available sources (http://www.uniprot.org/help/uniparc) to ensure that complete coverage is available at a single site. To avoid redundancy, all sequences 100% identical over the entire length are merged, regardless of source organism. New and updated sequences are loaded on a daily basis, cross-referenced to the source database accession number, and provided with a sequence version that increments upon changes to the underlying sequence. The basic information stored within each UniParc entry is the identifier, the sequence, cyclic redundancy check number, source database(s) with accession and version numbers, and a time stamp. If a UniParc entry lacks a cross-reference to a UniProtKB entry, the reason for its exclusion from UniProtKB is provided (e.g. pseudogene). In addition, each source database accession number is tagged with its status in that database, indicating if the sequence still exists or has been deleted in the source database and cross-references to NCBI GI and TaxId if appropriate.
