Cysteine Sulfoxidation Increases the Photostability of Red Fluorescent Proteins

ACS Chem Biol. 2016 Oct 21;11(10):2679-2684. doi: 10.1021/acschembio.6b00579. Epub 2016 Sep 12.


Photobleaching of fluorescent proteins (FPs) is a major limitation to their use in advanced microscopy, and improving photostability remains highly challenging due to limited understanding of its molecular mechanism. Here we discovered a new mechanism to increase FP photostability. Cysteine oxidation, implicated in only photobleaching before, was found to drastically enhance FP photostability to the contrary. We generated a far-red FP mStable by introducing a cysteine proximal to the chromophore. Upon illumination, this cysteine was oxidized to sulfinic and sulfonic acids, enabling mStable more photostable than its ancestor mKate2 by 12-fold and surpassing other far-red FPs. mStable outperformed in laser scanning confocal imaging and super-resolution structured illumination microscopy. Moreover, photosensitization to oxidize a cysteine similarly introduced in another FP mPlum also increased its photostability by 23-fold. This postfolding cysteine sulfoxidation cannot be simply substituted by the isosteric aspartic acid, representing a unique mechanism valuable for engineering better photostability into FPs.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Cysteine / chemistry*
  • Luminescent Proteins / chemistry*
  • Photobleaching
  • Photochemical Processes
  • Protein Stability
  • Red Fluorescent Protein


  • Luminescent Proteins
  • Cysteine