GenBank Protein - A collection of sequences from several sources, including translations from annotated coding regions in GenBank, RefSeq and TPA, as well as records from SwissProt, PIR, PRF, and PDB.

PDB - An information portal to biological macromolecular structures

RefSeq - A comprehensive, integrated, non-redundant, well-annotated set of reference sequences including genomic, transcript, and protein.

UniProt/Swiss-Prot - Manually annotated and reviewed records of protein sequence and functional information