Protein moonlighting
（重定向自Gene sharing）
![Crystallographic structure of cytochrome P450 from the bacteria S. coelicolor (rainbow colored cartoon, N-terminus = blue, C-terminus = red) complexed with heme cofactor (magenta spheres) and two molecules of its endogenous substrate epi-isozizaene as orange and cyan spheres respectively. The orange-colored substrate resides in the monooxygenase site while the cyan-colored substrate occupies the substrate entrance site. An unoccupied moonlighting terpene synthase site is designated by the orange arrow.[1]](/Images/godic/202501/15/3EL34435.png")
![Crystallographic structure of aconitase[12]](/Images/godic/202501/15/PDB_1aco_EBI4435.jpg")
![A crystallin from ducks that exhibits argininosuccinate lyase activity and is a key structural component in eye lenses, an example of gene sharing](/Images/godic/202501/15/Duck_Delta_1_Crystallin4435.jpg")
Protein moonlighting (or gene sharing) is a phenomenon by which a protein can perform more than one function. Ancestral moonlighting proteins originally possessed a single function but through evolution, acquired additional functions. Many proteins that moonlight are enzymes; others are receptors, ion channels or chaperones. The most common primary function of moonlighting proteins is enzymatic catalysis, but these enzymes have acquired secondary non-enzymatic roles. Some examples of functions of moonlighting proteins secondary to catalysis include signal transduction, transcriptional regulation, apoptosis, motility, and structural.