title: Chromophore Deprotonation State Alters the Optical Properties of Blue Chromoprotein.
abstract: 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.
authors.affiliation: Institute of Molecular and Cellular Biology, National Taiwan University, Taipei, Taiwan.
authors.forename: Cheng-Yi
authors.initials: CY
authors.lastname: Chiang
authors.affiliation: Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan; Core Facility for Protein Production and X-ray Structural Analysis, Academia Sinica, Taipei, Taiwan.
authors.forename: Cheng-Chung
authors.initials: CC
authors.lastname: Lee
authors.affiliation: Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan; Core Facility for Protein Production and X-ray Structural Analysis, Academia Sinica, Taipei, Taiwan.
authors.forename: Shin-Yi
authors.initials: SY
authors.lastname: Lo
authors.affiliation: Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan; Core Facility for Protein Production and X-ray Structural Analysis, Academia Sinica, Taipei, Taiwan.
authors.forename: Andrew H-J
authors.initials: AH
authors.lastname: Wang
authors.affiliation: Institute of Biomedical Sciences, MacKay Medical College, New Taipei City, Taiwan.
authors.forename: Huai-Jen
authors.initials: HJ
authors.lastname: Tsai
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D018360:Crystallography, X-Ray; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism*; D008164:Luminescent Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009154:Mutation / Q000235:genetics; D010860:Pigments, Biological / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011487:Protein Conformation; D015202:Protein Engineering; D012615:Sea Anemones / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D015027:Zebrafish / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*
chemical_list: D008164:Luminescent Proteins; D010860:Pigments, Biological; D049452:Green Fluorescent Proteins