Moonlighting Proteins: Proteins with Multiple Functions

Moonlighting proteins, also referred to as ‘gene sharing’, refer to a subset of multifunctional proteins in which two or more different functions are performed by one polypeptide chain, and the multiple functions are not a result of splice variants, gene fusions, or multiple isoforms [1]. In addition, they do not include proteins with the same function in multiple locations or protein families in which different members have different functions, if each individual member has only one function. A single protein with multiple functions may seem surprising, but there are actually many cases of proteins that ‘moonlight’.