A mosaic protein is a protein that is made up of different protein domains, giving the protein multiple functions. These proteins have quaternary structures, as they are made up of multiple tertiary structured protein domains. Protein domains can combine to form different types of proteins, creating a diversity of proteins.[1] These domains are spread throughout the genome because they are mobile, which is why some domains can be found in a variety of proteins, even though they are seemingly unrelated. This also allows the domains to fold independently, and so they don't become deformed and unfolded in a new environment.[2]
Whereas many proteins are encoded by a single gene, many others get peptide chains from several genes; it is the nature of mosaic proteins that they are always polygenic.