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PubMed2004

Kinetic analysis and modeling of firefly luciferase as a quantitative reporter gene in live mammalian cells.

Firefly luciferase has proven to be a highly sensitive and quantitative reporter gene for studying gene delivery and regulation, and its recent use in live cells and organisms promises to further expand its utility. However, the intracellular behavior and properties of the enzyme are not well characterized. Specifically, information on the intracellular kinetics and stability of luciferase activity is necessary for real-time luminescence counts from live cells to be quantitatively meaningful. Here, we report a dynamic analysis of luciferase activity in the context of living mammalian cells. We have determined the relative light units measured in living cells to be proportional to that found in cell lysate. We have also calculated the K(m) of luciferase in living cells to be approximately 1 mM, a value much higher than the 10 microM found for pure enzyme in vitro. In addition, a 2-hour half-life of luciferase activity in live cells was measured in real time. Finally, we have modeled luciferase activity in live cells for the purposes of understanding and translating the luciferase signal into a more effective metric of gene expression and cell behavior.

Animals↗

PubMed2003

Development of a dual-luciferase fusion gene as a sensitive marker for site-directed DNA repair strategies.

BACKGROUND: Several novel techniques have been developed recently for the site-specific repair of DNA as an approach to gene therapy. Correction efficiencies as high as 40% have been reported, well within the range of therapeutic impact for a number of genetic diseases. Unfortunately, many of the model systems in which these methods have been employed typically target genes that are not well suited for analyzing the various techniques. METHODS: To address this, we have constructed and characterized a dual-luciferase fusion gene as a sensitive marker for optimizing repair strategies. The genes encoding two distinct luciferase proteins were fused so that expression of one luciferase necessitated expression of the other. Engineering a stop codon in the downstream luciferase gene created an ideal tool to study the efficiency of various site-directed DNA repair techniques as one luciferase can act as an internal control while the other is targeted for correction. RESULTS: Fusing two luciferase genes resulted in a single protein that produces two bioluminescent activities in a constant ratio. The utility of this system as a target for site-directed DNA repair research was demonstrated using two of the recently developed gene repair techniques, small fragment homologous replacement and oligonucleotide-mediated repair, to mediate correction and by the ability to detect repair efficiencies of less than 5 x 10(-6) (<1 event in 200000). CONCLUSIONS: The ability to rapidly and accurately quantify the amount of correction using the dual-luciferase fusion system will allow the comparison and evaluation of the many factors involved in successful gene repair and lead to the optimization of these techniques, both in cell culture and in whole animals.

Amino Acid Sequence↗

PubMed2002

Real-time imaging of beta-lactoglobulin-targeted luciferase activity in the mammary glands of transgenic mice.

This study was aimed at establishing a new platform for real-time monitoring of milk-protein gene expression in the mammary glands. A transgenic reporter composed of the beta-lactoglobulin (BLG)/luciferase hybrid gene was targeted to the mammary glands of pregnant and lactating mice and luciferase activity was imaged in vivo with a low-light imaging system. The mammary glands of a 17-day pregnant mouse occupied an area comparable to that of a 6-day lactating mouse. Nevertheless, the intensity of the luciferase signal was much weaker and confined to regions in the inguinal and thoracic glands. A few small and defined locations of higher expression were also detected, indicating diversity in the initiation of this transgenic milk protein expression. In the lactating mice, high inter- and intra-heterogeneity among regions in a particular gland and among glands was demonstrated, and confirmed by ex vivo analysis of luciferase activity in mammary biopsies. The lack of correlation between luciferase activities and levels of beta-casein accumulation in these biopsies resulted, most probably, from the longer half-life of the native milk protein, compared to the activity of the transgenic marker in the tissue. Unilateral sealing of mammary glands for 4 hr resulted in complete abrogation of luciferase activity, establishing the BLG/luciferase transgene as a reliable tool to follow short-term stimuli. Dispersed mammary epithelial cells preserved luciferase activity in culture, and thus could be used for following mammary gland development after re-implantation. The bioluminescence-based methodology presented here eliminates averaging of heterogeneity in gene expression among glands, and misinterpretations resulting from sampling biopsies taken from inactive regions. Imaging luciferase expression in the mammary glands may enable an accurate monitoring of milk-protein gene expression during cyclic periods of development and apoptosis in a limited number of animals, and could be applied for reporting the consequences of selected drugs on milk-protein gene expression.

Animals↗

PubMed1997

Inactivation of firefly luciferase with N-(iodoacetyl)-N'- (5-sulfo-1-naphthyl)ethylenediamine (I-AEDANS).

N-Iodoacetyl-N'-(5-sulfo-1-naphthyl)ethylenediamine (I-AEDANS), a fluorescent reagent that selectively modifies cysteine residues, was demonstrated to irreversibly inhibit native Photinus pyralis luciferase purified from firefly lanterns. Complete inactivation of luciferase activity was accompanied by the blockage of all four cysteine thiols and the concomitant incorporation of 4 mol of N-acetyl-N'-(5-sulfo-1-naphthyl)ethylenediamine (AEDANS) per mole of enzyme. Employing proteolytic digestions of AEDANS-labeled luciferase and reverse-phase-high-performance liquid chromatography (RP-HPLC), seven tagged peptides were isolated. The AEDANS label provided a convenient spectroscopic marker for the identification of the modified peptides. The sequences of the labeled peptides were deduced from electrospray ionization mass spectrometry (ESMS) and N-terminal sequencing. The fluorescent peptides included cysteine residues and spanned sequences composed of amino acids Leu78-Lys85, Thr214-Arg218, Asp224-Arg275, and Gly388-Met396. The luciferin substrate provided substantial protection against luciferase inactivation resulting in a 60-67% decrease in the labeling of all four cysteine thiols. Thus, it does not appear that a specific cysteine mediates the loss of luciferase activity. Additional LC/ESMS studies permitted the identification of 78% of the native luciferase molecule, which, unlike the recombinant protein, was found to contain an acetylated N-terminus. The AEDANS labeling results and the identification of well-defined proteolytic fragments should facilitate future structure-function investigations of the firefly luciferases.

Adenosine Triphosphate↗

PubMed1992

Molecular cloning and expression in Escherichia coli of a cDNA clone encoding luciferase of a firefly, Luciola lateralis.

We have cloned a cDNA encoding Luciola lateralis (a common firefly in Japan) luciferase from a cDNA library of lantern poly(A)+ RNA, using a cDNA of L. cruciata (another common firefly in Japan) luciferase as a probe. The primary structure of L. lateralis luciferase deduced from the nucleotide sequence was shown to consist of 548 amino acids with a molecular weight of 60,132. Sequence comparison indicates that L. lateralis luciferase has significant sequence identity (94%) to L. cruciata luciferase, and that it has less sequence similarity (67%) to Photinus pyralis (a North American firefly) luciferase. The isolated cDNA clone, when introduced into Escherichia coli, directed the synthesis of enzymatically active luciferase under the control of the lacZ promoter.

Amino Acid Sequence↗

PubMed2006

Luciferase from the Italian firefly Luciola italica: molecular cloning and expression.

The cDNA encoding the luciferase from the Italian firefly Luciola italica was cloned using reverse transcriptase-PCR and a gene-specific primer set based on the DNA sequence of Luciola mingrelica. The cDNA sequence of L. italica luciferase was determined to be 1647 base pairs in length with an open reading frame of 548 amino acids. Phylogenetic analysis of the protein sequence demonstrated that this luciferase is closely related to that of other fireflies of the Lampyridae family, particularly within the Luciolinae subfamily, showing 96% homology to luciferases from the fireflies Hotaria unmunsana and Hotaria parvula. The specific activity of the L. italica luciferase was 78% of the North American enzyme, after correction for emission color differences. The bioluminescence emission of the Italian firefly is pH sensitive with maxima at 566 nm and 614 nm at pH 7.8 and 6.0, respectively. Interestingly, the total bioluminescence output was approximately 2-fold greater than that of P. pyralis luciferase due to differences in turnover characteristics evidenced by extended light emission decay kinetics. We expect that this newly discovered luciferase will be suitable for a wide range of bioluminescence applications including in vivo imaging and multiplex assays.

Amino Acid Sequence↗

PubMed2005

Identification of paralogous genes of firefly luciferase in the Japanese firefly, Luciola cruciata.

Two homologous genes of firefly luciferase, LcLL1 and LcLL2, were cloned from the Japanese firefly Luciola cruciata, and were expressed and characterized. The gene product of LcLL1 had long-chain fatty acyl-CoA synthetic activity, but not luciferase activity. The other gene product of LcLL2 did not show enzymatic activities of acyl-CoA synthetase and luciferase. RT-PCR analysis showed that the transcript of LcLL1 was abundant in larva but very low in adult, while LcLL2 was expressed in both larva and adult. Phylogenetic analysis indicated that LcLL1 and LcLL2 are paralogous genes of firefly luciferase. Recently, we found that CG6178 in Drosophila melanogaster is an orthologue of firefly luciferase and shows fatty acyl-CoA synthetic activity, but not luciferase activity. These results suggest that firefly luciferase might be evolved from a fatty acyl-CoA synthetase by gene duplication in insects.

Amino Acid Sequence↗

PubMed2002

Generation of thermostable monomeric luciferases from Photorhabdus luminescens.

Bacterial luciferases and the genes encoding these light-emitting enzymes have an increasing number of applications in biological sciences. Temperature lability and the heterodimeric nature of these luciferases have been the major obstacles for their widespread use, for instance, as genetic reporters. Escherichia coli expressing wild-type Photorhabdus luminescens luciferase was found to produce eight times more light than the corresponding Vibrio harveyi luciferase clone in vivo at 37 degrees C. Three monomeric luciferases were created by translationally fusing the two genes encoding luxA and luxB proteins of P. luminescens. These clones were equally active in producing light in vivo when cultivated at 37 degrees C compared to cultivation at 30 degrees C. The fusion containing the longest linker showed the highest activity. In vitro, the monomeric luciferases were less active having at best 20% of activity of the wild-type enzyme due to the partial formation of insoluble aggregates. The results suggest that P. luminescens luciferase and monomeric derivatives thereof should be more suitable than the corresponding V. harveyi enzyme to be used as reporters in cell types which need cultivation at elevated temperatures.

Enzyme Stability↗

PubMed1995

Involvement of MAP kinase in insulin signalling revealed by non-invasive imaging of luciferase gene expression in single living cells.

BACKGROUND: Studies of the mechanisms by which signals are transmitted from receptor tyrosine kinases would be facilitated by a way of monitoring events at the single-cell level. We have explored how luciferase imaging can be used to examine the role of specific signalling pathways in insulin-stimulated gene expression. The analysis of luciferase expression in single cells has previously been hampered by the insensitivity of existing methodologies and the lack of a way of monitoring quantitatively, and independently, more than one promoter within the same cell. We have developed a technique for examining the dynamics of insulin-stimulated AP-1-dependent transcription in single living cells, and have explored the signalling pathway involved. RESULTS: Luciferase and aequorin gene expression were examined in single living cells with a high-sensitivity photon-counting camera. The technique involved the comicroinjection of luciferase- and aequorin-based reporter plasmids directly into the cell nucleus, and the subsequent analysis of luminescence in the presence of luciferin and coelenterazine, respectively. The method is quantitative and allows insulin-stimulated gene expression to be monitored in real time. We found that insulin promoted a substantial increase in the expression of a luciferase gene under the control of the AP-1-binding site from the collagenase gene promoter. Aequorin expression, under the control of a cytomegalovirus promoter, was unaffected by insulin. The effect of insulin on luciferase expression was specifically blocked by overexpression of either the mitogen-activated protein (MAP) kinase phosphatase CL100, or the dominant-negative mutant MAP kinase kinase, MEKS217/221A. CONCLUSIONS: Microinjection coupled with luciferase imaging allows hormone-regulated gene expression from relatively weak promoters to be monitored in single living cells. We have used this method to demonstrate that MAP kinase plays a central role in the ability of insulin to stimulate AP-1-dependent gene transcription.

Aequorin↗

PubMed1999

A streptavidin-luciferase fusion protein: comparisons and applications.

Luciferases are unique enzymes in being capable of emitting visible light as one of the end-products of their catalysis. Both procaryotic and eucaryotic organisms exist that emit light, and the luciferases from these organisms differ considerably in size as well as chemistry of catalysis. Two main, i.e. most studied groups, are the bacterial luciferases of e.g. Vibrio fisheri, Vibrio harveyi, and Photorhabdus luminescens, responding to FMNH2, long-chain aldehyde and molecular oxygen and the insect luciferases of the fireflies Photinus pyralis and Luciola minengrelica or click beetle Pyrophorus plagiophthalamus, responding to ATP, luciferin and molecular oxygen. An emerging amount of 'new' luciferases from shrimps, fish, jelly fish and overall from marine origin, are finding their way to biotechnological applications. The common feature of these is their ability to produce light within the visible region of the spectrum, i.e. between 450 nm (blue) and 630 nm (red). In this short review, we discuss some of the recent advances on fusion proteins of eucaryotic luciferases and their applications. Special emphasis is placed on a streptavidin-luciferase fusion protein produced by insect cells using the baculovirus expression system.

Animals↗

PubMed1980

Formation of hybrid luciferases from subunits of different species of Photobacterium.

Enzyme divergence within three species of the genus Photobacterium (P. fischeri, P. leiognathi, and P. phosphoreum) was studied by comparing the catalytic characteristics and quaternary interactions of bacterial luciferases isolated from each species. Each luciferase was composed of two subunits of different molecular weights as determined by sodium dodecyl sulfate--polyacrylamide gel electrophoresis. Subunits were isolated in quantity by DEAE-Sephadex gel filtration in 7 M urea. Isolated subunits had no luciferase activity after renaturation in buffer, but active enzyme could be recovered by renaturation of the heavy and light subunits together. Renaturation of hybrid pairs (containing one subunit from each of two different species) yielded active luciferases, but only in cases where a heavy subunit of one species was combined with a light subunit of another. These hybrids exhibited in vitro catalytic characteristics most like those of the parent luciferase from which the heavy subunit was derived. The light subunit of P. leiognathi luciferase conferred an increased thermal stability to all enzymes containing it. The heavy subunit of each of the three Photobacterium species was sensitive to trypsinization. Thus, on the basis of structural and functional analogies with the luciferase from Beneckea harveyi, the heavy and light subunits of Photobacterium species have been designated alpha and beta, respectively.

Chromatography, Ion Exchange↗

PubMed1978

Structural studies on bacterial luciferase using energy transfer and emission anisotropy.

The distance between specific sites on bacterial luciferase was estimated by energy transfer. Luciferase was fluorescently labeled by reaction of an essential sulfhydryl group with N-(1-pyrene)maleimide and N-[p-(2-benzoxazolyl)phenyl]meleimide. Both of the modified enzymes bind 8-anilino-1-naphthalenesulfonate (Ans) with affinities similar to that exhibited by the native luciferase. Using each of the two fluorescent probes as a donor and the bound Ans as an acceptor, the energy transfer efficiencies were determined by the resulting enhancement of fluorescence of the acceptor. The corresponding distance was calculated to be in the range of 21 to 37 A. Energy-transfer studies were also carried out using fluorescence lifetime measurements of bound ANS, acting as a donor with bound FMN as an acceptor. The corresponding distance was calculated to be between 30 and 58 A. Using samples of luciferase:Ans complex and luciferase modified with N-(1-pyrene)maleimide, the rotational correlation time of the enzyme-dye conjugate as awhole was found to be 47 +/- 2 ns. The observed rotational correlation time is much longer than that calculated for luciferase assuming a spherical structure, thus indicating an elongated form for the luciferase-dye conjugate.

Anilino Naphthalenesulfonates↗

PubMed1975

Photoexcited bacterial luminescence. Spectral properties and mechanistic implication of a reduced flavine-like prosthetic group associated with photoexcitable luciferase.

A prosthetic group, designated B, has been isolated from bacterial photoexcitable luciferase and found to possess spectral and photochemical properties characteristic of substituted reduced flavines. Its fluorescence when bound to luciferase has an excitation maximum at 375 nm, correlating well with the absorption spectrum, and an emission peaking at 495 nm. However, free B is nonfluorescent in aqueous solution at ambient temperature. Both free and luciferase-bound B show similar negative circular dichroism in the region 330-475 nm with troughs at 375 and 380 nm, respectively. In the luciferase reaction initiated by FMNH2, B is an inhibitor competitive with FMNH2. Irradiation of photoexcitable luciferase converts B to FMN, the latter identified spectrally, enzymatically, and chromatographically. These findings lead to the suggestion that B is a substituted FMNH2. The luciferase-bound B resembles but is not identical with the normal flavine intermediate obtainable by reacting luciferase with reduced flavine mononucleotide and oxygen. It is hypothesized that B is a false intermediate of the bacterial bioluminescence reaction, and a mechanism for the photoexcited bioluminescence reaction is suggested.

Binding Sites↗

PubMed1975

Differential effects of 8-anilino-1-naphthalenesulfonate upon binding of oxidized and reduced flavines by bacterial luciferase.

Upon binding to bacterial luciferase, both the absorption and the fluorescence excitatiom maxima of 8-anilino-1-naphthalensulfonate (ANS) shift from 353 to 370 nm while the fluorescence emission optimum shifts from 540 to 480 nm, and the fluorescence quantum yield increases from 0.003 to 0.39, indicating that the environment of the ANS binding site is hydrophobic. ANS binds to luciferase with dissociation constants of 1.9 X 10(-5) and 2.3 X 10(-5) M at 5 and 23 degrees, repsectively. As with both oxidized flavine mononucleotide (FMN) and reduced flavine mononucleotide (FMNH2), ANS also binds to luciferase with a stoichiometry of 1 site per dimeric luciferase molecule. ANS acts as a luciferase inhibitor, competitive with FMNH2, with an inhibitor constant of 2.3 X 10(-5) M at 23 degrees. However, the binding of ANS does not significantly displace FMN from binding to luciferase. Interactions of FMN and FMNH2 with luciferase are thus differentially regulated by the ANS binding.

Anilino Naphthalenesulfonates↗

PubMed2001

Members of a dinoflagellate luciferase gene family differ in synonymous substitution rates.

Regulation and evolution of dinoflagellate luciferases are of particular interest since the enzyme is structurally unique and bioluminescence is under circadian control. In this study, three new members of the dinoflagellate luciferase gene family were identified and characterized from Pyrocystis lunula. These genes, lcfA, lcfB, and lcfC, also exhibit the unusual structure and organization previously reported for the luciferase gene of a related dinoflagellate, Lingulodinium polyedrum: three repeated domains, each encoding an active catalytic site, multiple gene copies, and tandem organization. The histidine residues involved in the pH regulation of L. polyedrum luciferase activity, and implicated in the regulation of flashing, are also fully conserved in P. lunula. The interspecific conservation between the individual luciferase domains of P. lunula and L. polyedrum is higher than among domains intramolecularly, indicating that this unique gene structure arose through duplication events that occurred prior to the divergence of these dinoflagellates. However, P. lunula luciferase genes differ from L. polyedrum in several respects, notably, the occurrence of an intron in one gene (lcfC), a 2.25-kb intergenic region connecting lcfA and lcfB, and, of particular interest, an invariant rate of synonymous (silent) substitutions along the repeat domains, in contrast to L. polyedrum luciferase, where the occurrence of synonymous substitutions is practically absent in the central region of the domains.

Amino Acid Sequence↗

PubMed2005

Probing the functionalities of alphaGlu328 and alphaAla74 of Vibrio harveyi luciferase by site-directed mutagenesis and chemical rescue.

This work aimed at identifying essential residues on the alpha subunit of Vibrio harveyi luciferase and elucidating their functional roles. Four conserved alpha-subunit residues at the proposed luciferase active site were initially mutated to Ala. Screening of the in vivo bioluminescence of cells expressing these mutated luciferases allowed the work to focus on alphaGlu328 for additional mutations to Phe, Leu, Gln, His, and Asp. V. harveyi luciferase is known to contain, at the same proposed active site, an unusual cis-peptide linkage between alphaAla74 and alphaAla75. To explore the structure-function relationship, luciferase variants alphaA74F and alphaA74G were constructed. The six alphaGlu328-mutated and the two alphaAla74-mutated luciferase variants were purified and characterized with respect to Vmax, Michaelis constants, light and dark decays, quantum yield, and, for alphaE328F and alphaA74F, yield of the 4a-hydroperoxyFMN intermediate and the ability to oxidize aldehyde substrate. Results indicated that the structural integrities of both alphaGlu328 and alphaAla74 were essential to luciferase bioluminescence activity. Moreover, the essentiality of alphaGlu328 was linked to the acidic nature of its side chain. The low activity of alphaE328A was sensitive to chemical rescue by sodium acetate, an effect that was not reproduced by phosphate. The efficiency of activity rescue by acetate progressively increased at lower pH in the range from 6.0 to 8.0, supporting the interpretation of alphaGlu328 as a catalytic general acid. The rescuing effect of acetate was on a reaction step after the formation of the 4a-hydroperoxyFMN intermediate. The exact catalytic function of alphaGlu328 is unclear, but possibilities are discussed.

Alanine↗

PubMed1998

Mechanism of reduced flavin transfer from Vibrio harveyi NADPH-FMN oxidoreductase to luciferase.

The mechanisms of reduced flavin transfer in biological systems are poorly understood at the present. The Vibrio harveyi NADPH-FMN oxidoreductase (FRP) and the luciferase pair were chosen as a model for the delineation of the reduced flavin transfer mechanism. FRP, which uses FMN as a cofactor to mediate the reduction of the flavin substrate by NADPH, exhibited a ping-pong kinetic pattern with a Km, FMN of 8 microM and a Km,NADPH of 20 microM in a single-enzyme spectrophotometric assay monitoring the NADPH oxidation. However, the kinetic mechanism of FRP was changed to a sequential pattern with a Km,FMN of 0.3 microM and a Km,NADPH of 0.02 microM in a luciferase-coupled assay measuring light emission. In contrast, the Photobacterium fischeri NAD(P)H-FMN oxidoreductase FRG showed the same ping-pong mechanism in both the single-enzyme spectrophotometric and the luciferase-coupled assays. Moreover, for the FRP, FMN at concentrations over 2 microM significantly inhibited the coupled reaction in both light intensity and quantum yield, and showed apparent noncompetitive and competitive inhibition patterns against NADPH and luciferase, respectively. No inhibition of the NADPH oxidation was detected under identical conditions. These results are consistent with a scheme that the reduced flavin cofactor of FRP is preferentially utilized by luciferase for light emission, the reduced flavin product generated by the reductase is primarily channeled into a dark oxidation, and luciferase competes against flavin substrate in reacting with the FRP reduced flavin cofactor. An FRP derivative containing 2-thioFMN as the cofactor was also used to further examine the mechanism of flavin transfer. Results again indicate a preferential utilization of the reductase reduced flavin cofactor by luciferase for the bioluminescence reaction.

Apoenzymes↗

PubMed2004

Comparison of functional profiles at human recombinant somatostatin sst2 receptor: simultaneous determination of intracellular Ca2+ and luciferase expression in CHO-K1 cells.

1. Somatostatin (somatotropin release inhibiting factor; SRIF) acts via five G protein-coupled receptors (sst(1)-sst(5)) that modulate multiple cellular effectors. The aim of this study was to compare two functional effects of the human sst(2) receptor stably expressed in CHO-K1 cells in a single experiment using a duplex assay for intracellular calcium and serum response element (SRE)-driven luciferase expression. 2. Intracellular calcium was measured using a fluorometric imaging plate reader II (FLIPR II). SRIF-14 rapidly and transiently increased intracellular calcium with a pEC(50) of 8.74+/-0.03 (n=52). At 5 h after FLIPR II measurements, luciferase expression was determined. SRIF-14 concentration-dependently increased luciferase expression (pEC(50)=9.06+/-0.03, n=52). 3. Natural and synthetic agonist/antagonist ligands for SRIF receptors were tested in the duplex assay. Correlation of agonist potencies and efficacies between the two responses were significant (r(2)=0.83 and 0.90, pEC(50) and E(max), respectively). 4. Pertussis toxin pretreatment reduced SRIF-14/octreotide-mediated intracellular calcium increases by 45-47% and luciferase expression by 95-98%. 5. Thapsigargin pretreatment abolished the SRIF-14/octreotide-mediated intracellular calcium increase but had no effect on luciferase expression. 6. In conclusion, SRIF stimulates an increase in intracellular calcium and SRE-luciferase expression via human sst(2) receptors in CHO-K1 cells. The increase in luciferase is mediated via G(i)/G(o) while intracellular calcium increase is mediated by both G(i)/G(o) proteins and pertussis toxin-insensitive G proteins, and is mainly via release of calcium from intracellular stores. SRIF ligands display a similar recognition profile suggesting that the ligand/receptor/G protein/effector interaction is similar for the two parameters.

Animals↗