Structural characterization of acylimine-containing blue and red chromophores in mTagBFP and TagRFP fluorescent proteins

Chem Biol. 2010 Apr 23;17(4):333-41. doi: 10.1016/j.chembiol.2010.03.005.


We determined the 2.2 A crystal structures of the red fluorescent protein TagRFP and its derivative, the blue fluorescent protein mTagBFP. The crystallographic analysis is consistent with a model in which TagRFP has the trans coplanar anionic chromophore with the conjugated pi-electron system, similar to that of DsRed-like chromophores. Refined conformation of mTagBFP suggests the presence of an N-acylimine functionality in its chromophore and single C(alpha)-C(beta) bond in the Tyr64 side chain. Mass spectrum of mTagBFP chromophore-bearing peptide indicates a loss of 20 Da upon maturation, whereas tandem mass spectrometry reveals that the C(alpha)-N bond in Leu63 is oxidized. These data indicate that mTagBFP has a new type of the chromophore, N-[(5-hydroxy-1H-imidazole-2-yl)methylidene]acetamide. We propose a chemical mechanism in which the DsRed-like chromophore is formed via the mTagBFP-like blue intermediate.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Crystallography, X-Ray
  • Luminescent Proteins / chemistry*
  • Luminescent Proteins / genetics
  • Models, Molecular
  • Mutation
  • Protein Conformation
  • Red Fluorescent Protein


  • Luminescent Proteins

Associated data

  • PDB/3M22
  • PDB/3M24