title: Site-directed mutagenesis of firefly luciferase: implication of conserved residue(s) in bioluminescence emission spectra among firefly luciferases.
abstract: The bioluminescence colours of firefly luciferases are determined by assay conditions and luciferase structure. Owing to red light having lower energy than green light and being less absorbed by biological tissues, red-emitting luciferases have been considered as useful reporters in imaging technology. A set of red-emitting mutants of Lampyris turkestanicus (Iranian firefly) luciferase has been made by site-directed mutagenesis. Among different beetle luciferases, those from Phrixothrix (railroad worm) emit either green or red bioluminescence colours naturally. By substitution of three specific amino acids using site-specific mutagenesis in a green-emitting luciferase (from L. turkestanicus), the colour of emitted light was changed to red concomitant with decreasing decay rate. Different specific mutations (H245N, S284T and H431Y) led to changes in the bioluminescence colour. Meanwhile, the luciferase reaction took place with relative retention of its basic kinetic properties such as K(m) and relative activity. Structural comparison of the native and mutant luciferases using intrinsic fluorescence, far-UV CD spectra and homology modelling revealed a significant conformational change in mutant forms. A change in the colour of emitted light indicates the critical role of these conserved residues in bioluminescence colour determination among firefly luciferases. Relatively high specific activity and emission of red light might make these mutants suitable as reporters for the study of gene expression and bioluminescence imaging.
authors.affiliation: Department of Genetics, Faculty of Basic Sciences, Tarbiat Modares University, Tehran, Iran.
authors.forename: Narges Kh
authors.initials: NKh
authors.lastname: Tafreshi
authors.forename: Majid
authors.initials: M
authors.lastname: Sadeghizadeh
authors.forename: Rahman
authors.initials: R
authors.lastname: Emamzadeh
authors.forename: Bijan
authors.initials: B
authors.lastname: Ranjbar
authors.forename: Hossein
authors.initials: H
authors.lastname: Naderi-Manesh
authors.forename: Saman
authors.initials: S
authors.lastname: Hosseinkhani
mesh_terms: D000818:Animals; D017124:Conserved Sequence / Q000502:physiology*; D048888:Fireflies / Q000201:enzymology / Q000235:genetics*; D017930:Genes, Reporter; D007700:Kinetics; D049409:Luciferases, Firefly / Q000737:chemistry / Q000235:genetics*; D008163:Luminescent Measurements; D008164:Luminescent Proteins / Q000138:chemical synthesis / Q000737:chemistry / Q000235:genetics / Q000502:physiology; D008954:Models, Biological; D016297:Mutagenesis, Site-Directed; D050505:Mutant Proteins / Q000138:chemical synthesis / Q000737:chemistry / Q000235:genetics; D011489:Protein Denaturation; D017386:Sequence Homology, Amino Acid; D013057:Spectrum Analysis; D000097573:Red Fluorescent Protein
chemical_list: D049409:Luciferases, Firefly; D008164:Luminescent Proteins; D050505:Mutant Proteins; D000097573:Red Fluorescent Protein