Analysis of amino acid sequences from different organisms often reveals cases in which two or more proteins encoded for separately in a genome also appear as fusions, either in the same genome or that of some other organism. Such fusion proteins, termed Rosetta stone sequences, help link disparate proteins together, and suggest the likelihood of functional interactions between the linked entities, describing local and global relationships within the proteome. These relationships help us understand the role of proteins within the context of their associations, and facilitate assignment of putative functions to uncharacterized proteins based on their linkages with proteins of known function.