# mSumireF a Monomeric Violet Fluorescent Protein

## TL;DR

Scientists created a brighter violet fluorescent protein that works well in cells and pairs with other colors for experiments.

## Contribution

A new violet fluorescent protein, mSumireF, is developed with improved brightness and reduced dimerization.

## Key findings

- mSumireF brightness is restored by reverting a tyrosine to phenylalanine.
- mSumireF shows less oligomerization in mammalian cells and solution assays.
- mSumireF pairs effectively with other fluorescent proteins for FRET-based ATP biosensors.

## Abstract

The development of
genetically encoded labels for multicolor experiments
requires a diverse palette of fluorescent proteins that are well-behaved.
Here, we report mSumireF, a monomeric variant of the violet fluorescent
protein Sumire. On its own, the canonical monomerizing valine-to-lysine
mutation at residue 206 causes a significant loss of brightness for
the mSumire variant. We found that brightness is recovered upon the
reversion of mSumire’s tyrosine at position 165 back to phenylalanine
as in its superfolder GFP grandparent. Importantly, this mSumireF
variant exhibits significantly less oligomerization tendency in the
organized smooth endoplasmic reticulum (OSER) assay in mammalian cells
and in protein solution assays. Furthermore, we demonstrate that an
mSumireF donor can be effectively paired with the fluorescent protein
acceptors mCerulean3, mTurquoise2, and LSSmScarlet to generate FRET-based
ATP biosensors. mSumireF thus provides an improved violet fluorescent
protein to expand color options with reduced concern of unwanted dimerization.