NCBI protein database- It is a compilation of the protein sequence present in other databases. The NCBI database contains the entries from the swissprot, PIR database, PDB database and other known databases.

UniProt- EBI, SIB and Georgetown university together collected the protein information in the form of a centralized catalogue known as universal protein resource (UniProt). It contains the information about the 3-D structure, expression profile, secondary structures and biochemical function of the protein. UniProt consists of 3 parts: UniProt Knowledge database (UniProtKB), UniProt Reference (UniRef) and UniProt Archive (UniPArc). As discussed before, UniProtKB is a collection from SwissProt and TrEMBL database. UniRef is a nonredudant sequence database and it can allow to search similar sequences. UniRef 100, UniRef90 and UniRef50 are the three version of the database allow searching of sequences 100%, >90% and >50% identical ot the query sequence.