Protein Moonlighting
- Science Holic
- Sep 30
- 3 min read
Author: Ella Chen
Editors: Hwi-On Lee, Jonathan Chen
Artist: Felicia Chen
Proteins are often thought of as structures that only perform one specific function, with examples including hemoglobin, which transports oxygen, antibodies, which fight infections, and DNA polymerase, which synthesizes DNA molecules. However, recent studies have uncovered a number of proteins that are able to perform multiple functions, a process known as moonlighting. The discovery of these proteins provides a newer understanding to what is currently known about proteins and opens up new ways to study biological systems.
Moonlighting proteins were first discovered in the 20th century, when scientists observed that certain crystallins, which typically serve as structural proteins, also carried out enzymatic functions. This phenomenon was originally referred to as “gene sharing,” but is now called moonlighting. Protein moonlighting is believed to be a product of evolution; moonlighting allows for an organism to utilize one protein for multiple tasks which, in turn, saves space in the genome and conserves the energy needed to synthesize an entirely new protein. Proteins are able to moonlight due to structural flexibility in response to cellular changes in their environment. They can carry out different functions as a result of their location in the cell or the cell that it’s working with. It’s important to note that protein moonlighting is limited to proteins that perform multiple unrelated functions. Proteins created as a result of gene duplication or gene fusion are not considered moonlighting proteins because their ability to perform multiple functions is a result of genetics, not evolution. Another distinct characteristic of moonlighting proteins is that their functions are independent of each other, meaning that if one of the functions is inactivated (such as by mutation), the other functions will not be affected, allowing the protein to continue carrying out the unaffected functions.
Several commonly used proteins possess the ability to moonlight, and moonlighting proteins have been discovered in a variety of species ranging from yeast to animals. For instance, as mentioned earlier, crystallins are usually structural proteins found in the lens and cornea of the eye and they help maintain the lens’s transparency to allow for light to pass through. However, certain crystallins also have properties of enzymes, functioning as lactate dehydrogenase or as a glycolytic enzyme. Another example of a moonlighting protein is heat-shock proteins (HSPs). HSPs normally fold and refold proteins to maintain stability and prevent their degradation, but some HSPs have been found to play a role in the immune system by regulating the immune response. These examples demonstrate the multifunctionality of moonlighting proteins, as well as the vastly distinct tasks these proteins can carry out.
The discovery of protein moonlighting is still relatively recent, and there are many questions waiting to be answered regarding these proteins, such as how exactly they evolved, and how many proteins are moonlighting proteins. Since moonlighting proteins have been found in various kingdoms of life, it is evident they play a fundamental role in biological processes. Further research on the mechanisms behind these proteins could potentially lead to advances in drug design, as scientists can specifically alter the multiple functions of moonlighting proteins to treat diseases.
Citations:
Huberts, D. H. E. W., & van der Klei, I. J. (2010). Moonlighting proteins: An intriguing mode of
multitasking. Biochimica et Biophysica Acta (BBA) - Molecular Cell Research, 1803(4), 520–
Jeffery, C. J. (2014). An introduction to protein moonlighting. Biochemical Society Transactions,
42(6), 1679–1683. https://doi.org/10.1042/BST20140226
Jeffery, C. J. (2017). Protein moonlighting: what is it, and why is it important? Philosophical
Transactions of the Royal Society B: Biological Sciences, 373(1738), 20160523.
Comments