New bright-red fluorescent protein mScarlet to help with cellular staining

After years of trying, biologists have succeeded in creating an extremely bright red fluorescent protein in the lab. This is good news for researchers, including cancer and stem cell researchers, who use fluorescent proteins to track essential cellular processes. The researchers at the University of Amsterdam, the Institut de Biologie structurale and the European Synchrotron in Grenoble describe their approach in the latest edition of the journal Nature Methods.

Molecule structure protein mScarlet
Credit: Dr. Marten Postma, UvA
Professor of Molecular Cytology Dorus Gadella and doctoral researchers Daphne Bindels and Lindsay Haarbosch have succeeded in creating a spectacularly bright-red fluorescent protein. They have dubbed the protein mScarlet and expect it to be used by research groups across the world, for example to gain a better understanding of how disruption of cellular processes causes uncontrolled cell division found in cancer cells. 
The research group created mScarlet by comparing the genetic blueprints of a range of red fluorescent proteins from corals. They searched for sequences that consistently occurred in the various genetic codes since these apparently are indispensable. The group assembled these essential pieces of code and then had a company synthesise a complete DNA strand. They introduced that synthetic DNA into a bacterium, which converted it into a protein.

They assessed the brightness of each protein produced in this way under a microscope and then tinkered some more with the DNA code, observing how modifications affected the brightness. The entire process was a kind of lab-based evolutionary experiment which resulted in Gadella and his colleagues creating mScarlet, the protein with the highest brightness.

That brightness will serve cellular microscopy well as it ensures the visibility of the proteins studied by scientists. Moreover, mScarlet is an ideal illuminating agent as it does not affect the functioning of the proteins to which it is tagged.

In order to fully understand mScarlet, the biologists eventually sent their red creation to the Institut de Biologie Structurale in Grenoble. A team of researchers led by structural biologist Antoine Royant utilized the European Synchrotron Radiation Facility (ESRF), one of the most powerful particle accelerators in the world, to reveal the molecular structure of the protein. Royant: ‘We discovered that mScarlet’s bright fluorescence is due to fact that the chromophore, the part of the molecule that absorbs light and then emits red light, is held rigidly flat by the protein wrapped around it.’

Citation: “mScarlet: a bright monomeric red fluorescent protein for cellular imaging”. Daphne S Bindels, Lindsay Haarbosch, Laura van Weeren, Marten Postma, Katrin E Wiese, Marieke Mastop, Sylvain Aumonier, Guillaume Gotthard, Antoine Royant, Mark A Hink & Theodorus W J Gadella Jr. Nature Methods, 2016.
DOI: 10.1038/nmeth.4074
Adapted from press release by University of Amsterdam.