Chromophore Deprotonation State Alters the Optical Properties of Blue Chromoprotein

PLoS One. 2015 Jul 28;10(7):e0134108. doi: 10.1371/journal.pone.0134108. eCollection 2015.


Chromoproteins (CPs) have unique colors and can be used in biological applications. In this work, a novel blue CP with a maximum absorption peak (λmax) at 608 nm was identified from the carpet anemone Stichodactyla gigantea (sgBP). In vivo expression of sgBP in zebrafish would change the appearance of the fishes to have a blue color, indicating the potential biomarker function. To enhance the color properties, the crystal structure of sgBP at 2.25 Å resolution was determined to allow structure-based protein engineering. Among the mutations conducted in the Gln-Tyr-Gly chromophore and chromophore environment, a S157C mutation shifted the λmax to 604 nm with an extinction coefficient (ε) of 58,029 M-1·cm-1 and darkened the blue color expression. The S157C mutation in the sgBP chromophore environment could affect the color expression by altering the deprotonation state of the phenolic group in the chromophore. Our results provide a structural basis for the blue color enhancement of the biomarker development.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Crystallography, X-Ray
  • Green Fluorescent Proteins / genetics
  • Green Fluorescent Proteins / metabolism*
  • Luminescent Proteins / chemistry
  • Luminescent Proteins / genetics
  • Luminescent Proteins / metabolism*
  • Models, Molecular
  • Molecular Sequence Data
  • Molecular Structure
  • Mutation / genetics
  • Pigments, Biological / chemistry
  • Pigments, Biological / genetics
  • Pigments, Biological / metabolism*
  • Protein Conformation
  • Protein Engineering*
  • Sea Anemones / chemistry
  • Sea Anemones / genetics
  • Sea Anemones / metabolism*
  • Sequence Homology, Amino Acid
  • Zebrafish / genetics
  • Zebrafish / growth & development
  • Zebrafish / metabolism*


  • Luminescent Proteins
  • Pigments, Biological
  • Green Fluorescent Proteins

Grants and funding

This work was supported by the National Science Council, Taiwan (NSC103-2313-B-002-048-MY2). This work was also supported by Academia Sinica with grants from the National Science Council of Taiwan (NSC102-2319-B-001-003). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.