Structural basis for the phototoxicity of the fluorescent protein KillerRed

FEBS Lett. 2009 Sep 3;583(17):2839-42. doi: 10.1016/j.febslet.2009.07.041. Epub 2009 Jul 30.


The red fluorescent protein KillerRed, engineered from the hydrozoan chromoprotein anm2CP, has been reported to induce strong cytotoxicity through the chromophore assisted light inactivation (CALI) effect. Here, we present the X-ray structures of KillerRed in its native and bleached states. A long water-filled channel is revealed, connecting the methylene bridge of the chromophore to the solvent. This channel facilitates the transit of oxygen and of reactive oxygen species (ROS) formed by reaction with the excited chromophore. The functional roles of key mutations used to produce KillerRed are discussed, strong chromophore distortions in the bleached state are revealed, and mechanisms for ROS production and self protection are proposed. The presence of a partially mature, photo-resistant, green-emitting state is characterized, which accounts for enhanced CALI by "pre-bleached" KillerRed.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Crystallography, X-Ray
  • Dimerization
  • Hydrozoa
  • Light*
  • Luminescent Proteins / chemistry*
  • Luminescent Proteins / genetics
  • Luminescent Proteins / toxicity*
  • Models, Molecular
  • Protein Structure, Quaternary
  • Protein Structure, Tertiary
  • Reactive Oxygen Species / chemistry
  • Reactive Oxygen Species / metabolism


  • Luminescent Proteins
  • Reactive Oxygen Species