title: Effect of charge distribution in a flexible loop on the bioluminescence color of firefly luciferases.
abstract: Firefly luciferase is a monooxygenase that catalyzes the ATP-dependent conversion of firefly luciferin into a luciferyl-adenylate, which is oxidized to an electronically excited oxyluciferin in a multistep reaction and produces visible light with a remarkable quantum yield. The bioluminescence color of firefly luciferases is determined by the luciferase structure and assay conditions. Among different beetles, only luciferase from Phrixotrix railroad worm (Ph(RE)) emits red bioluminescence, naturally. The presence of Arg353 in Ph(RE) luciferase, which corresponds to the deleted residue in the other luciferases, is an important distinctive structural feature of it. Insertion of Arg356 into a green-emitter luciferase (Lampyris turkestanicus), corresponding to Arg353 in Phrixotrix hirtus, changed the emitted light from green to red. To further clarify the effect of this position on the light shift mechanism, four residues with similar sizes but different charges (Arg, Lys, Glu, and Gln) were inserted into Photinus pyralis luciferase, using site-specific insertion mutagenesis. Insertion of a residue with a positive side chain (Arg356 and Lys356) changed the light color to red, while insertion of a residue with a negative side chain (Glu356) had little effect on color. Insertion of a neutral residue (Gln356) at this position was performed without any change in bioluminescence spectra. Insertion of positively charged residues in this loop took place with a series of structural changes which were confirmed by fluorescence spectroscopy and homology modeling. Homology modeling reveals the appearance of a bulge in a flexible loop (T352-P359) upon mutation which shifts to the left side with a color change from green to red.
authors.affiliation: Department of Biochemistry, Faculty of Basic Sciences, Tarbiat Modares University, Tehran 14115-175, Iran.
authors.forename: Ali
authors.initials: A
authors.lastname: Moradi
authors.forename: Saman
authors.initials: S
authors.lastname: Hosseinkhani
authors.forename: Hossein
authors.initials: H
authors.lastname: Naderi-Manesh
authors.forename: Majid
authors.initials: M
authors.lastname: Sadeghizadeh
authors.forename: Bagher Said
authors.initials: BS
authors.lastname: Alipour
mesh_terms: D000595:Amino Acid Sequence; D000817:Anilino Naphthalenesulfonates / Q000378:metabolism; D003116:Color; D019295:Computational Biology; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation; D004795:Enzyme Stability; D007700:Kinetics; D049409:Luciferases, Firefly / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D008163:Luminescent Measurements; D008969:Molecular Sequence Data; D050505:Mutant Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D018583:Pliability; D011193:Potassium Iodide / Q000378:metabolism; D017433:Protein Structure, Secondary; D013050:Spectrometry, Fluorescence; D013057:Spectrum Analysis; D055672:Static Electricity; D013696:Temperature; D013997:Time Factors
chemical_list: C515594:8-anilino-1-naphthalenesulfonic acid; D000817:Anilino Naphthalenesulfonates; D050505:Mutant Proteins; D011193:Potassium Iodide; D049409:Luciferases, Firefly