mScarlet3 Protein: A New Tool for Imaging Living Cells

mScarlet3 is a type of red fluorescent protein that has been developed by researchers to label specific structures and organelles in cells. It is a monomeric protein, which means that it exists as a single molecule rather than forming aggregates.

The researchers used a targeted approach to evolve mScarlet-I, a previous version of the protein, to create mScarlet3. They made specific changes to the protein's amino acid sequence to improve its properties, such as increasing its brightness and quantum yield.

The crystal structure of mScarlet3 was also determined, which revealed a barrel-shaped structure with a hydrophobic patch of internal residues that helps to rigidify the protein.

One of the key advantages of mScarlet3 is its fast and complete maturation process. This means that it can be used to visualize cellular processes in real-time, which is important for studying dynamic processes such as cell division and migration.

mScarlet3 is also a useful tool for researchers because it can be used as a fusion tag to label specific structures in cells. Fusion tags are commonly used in molecular biology to study the localization and function of proteins. By fusing mScarlet3 to a protein of interest, researchers can visualize the protein in living cells and study its behavior in real-time.

In addition, mScarlet3 is a good acceptor for Förster resonance energy transfer (FRET), which is a technique used to study protein-protein interactions. FRET occurs when two fluorescent proteins are in close proximity, and energy is transferred from the donor protein to the acceptor protein. By fusing mScarlet3 to a protein of interest and using a donor protein that emits at a different wavelength, researchers can study protein-protein interactions in living cells.

mScarlet3 is also a good reporter in transient expression systems, which are used to study gene expression in cells. Transient expression systems involve introducing a plasmid containing a gene of interest into cells, which then express the protein encoded by the gene. By fusing mScarlet3 to the protein of interest, researchers can visualize the expression of the protein in real-time.

Several fusion constructs with mScarlet3 have been made to label specific cellular organelles and structures. For example, mScarlet3 has been fused to proteins that localize to the nucleus, mitochondria, and endoplasmic reticulum. In all instances, bright labeling of the correct structures and localizations was found.

Overall, mScarlet3 is a highly optimized red fluorescent protein that can be used as a powerful tool for studying cellular processes in real-time. Its fast and complete maturation process, combined with its high brightness and quantum yield, make it an ideal choice for imaging dynamic processes in living cells. Its ability to act as a fusion tag and FRET acceptor also make it a valuable tool for studying protein localization and interactions.


  1.  Bindels DS, Haarbosch L, van Weeren L, Postma M, Wiese KE, Mastop M, et al. mScarlet: a bright monomeric red fluorescent protein for cellular imaging. Nat Methods. 2017;14(1):53-56

  2.  Gadella TWJ Jr, van Weeren L, Stouthamer J, Hink MA, Wolters AHG, Giepmans BNG, et al. mScarlet3: a brilliant and fast-maturing red fluorescent protein. Nat Methods. 2023

Souce: NovoPro    2023-03-29