Recombinant Enhanced Green Fluorescent Protein Research Articles

Introduction of a plasmid and a protein into bovine and swine cells by water-in-oil droplet electroporation.

Instrument cost is a major problem for the transduction of DNA fragments and proteins into cells. Water-in-oil droplet electroporation (droplet-EP) was recently invented as a low-cost and effective method for the transfection of plasmids into cultured human cells. We here applied droplet-EP to livestock animal cells. Although it is difficult to transfect plasmids into bovine fibroblasts using conventional lipofection methods, droplet-EP enabled us to introduce an enhanced green fluorescent protein (EGFP)-expressing plasmid into bovine earlobe fibroblasts. The optimal transfection condition was 3.0 kV, which allowed 19.1% of the cells to be transfected. For swine earlobe fibroblasts, the maximum transfection efficacy was 14.0% at 4.0 kV. After transfection with droplet-EP, 69.1% of bovine and 76.5% of swine cells were viable. Furthermore, droplet-EP successfully transduced Escherichia coli recombinant EGFP into frozen-thawed bovine sperm at 1.5 kV. Flow cytometry analysis revealed that 71.5% of spermatozoa exhibited green fluorescence after transfection. Overall, droplet-EP is suitable for the transfection of plasmids and proteins into cultured livestock animal cells.

Purification of the recombinant enhanced green fluorescent protein from Escherichia coli using alcohol + salt aqueous two-phase systems

Abstract The enhanced green fluorescent protein (EGFP) is widely used as a marker in life science. Currently, purifications of the EGFP mostly involve chromatographic methods, which are multistep, time-consuming and costly. In the present study, the recombinant EGFP expressed in Escherichia coli was purified using an economic aqueous two-phase system (ATPS). Short-chain aliphatic alcohol and organic salt were chosen as the phase-forming components owing to their recyclability and biodegradability, respectively. The partition behaviour of EGFP was evaluated under the varying conditions of ATPS, including types and concentrations of phase-forming components, feedstock concentration, and pH. In an optimal primary 2-g ATPS comprising 1-propanol and tripotassium citrate, a high recovery of EGFP (i.e., 92.1%) was attained in the salt-rich bottom phase. To facilitate the easy recovery of purified EGFP, a secondary ATPS was used to back extract the EGFP to a new top ethanol-rich top phase, and the ethanol was removed from the purified EGFP via evaporation. The 1-propanol and ethanol used in the primary and secondary ATPSs (i.e. 20-g system) were successfully recycled in three successive rounds of EGFP purification, yielding the average EGFP purification factor of 11.34 and 75.7% of EGFP yield. The purification of EGFP using the two stages of alcohol + salt ATPSs is efficient in terms of operation time, cost and process scalability.

Enhanced green fluorescent protein-mediated synthesis of biocompatible graphene.

BackgroundGraphene is the 2D form of carbon that exists as a single layer of atoms arranged in a honeycomb lattice and has attracted great interest in the last decade in view of its physical, chemical, electrical, elastic, thermal, and biocompatible properties. The objective of this study was to synthesize an environmentally friendly and simple methodology for the preparation of graphene using a recombinant enhanced green fluorescent protein (EGFP).ResultsThe successful reduction of GO to graphene was confirmed using UV–vis spectroscopy, and FT-IR. DLS and SEM were employed to demonstrate the particle size and surface morphology of GO and EGFP-rGO. The results from Raman spectroscopy suggest the removal of oxygen-containing functional groups from the surface of GO and formation of graphene with defects. The biocompatibility analysis of GO and EGFP-rGO in human embryonic kidney (HEK) 293 cells suggests that GO induces significant concentration-dependent cell toxicity in HEK cells, whereas graphene exerts no adverse effects on HEK cells even at a higher concentration (100 μg/mL).ConclusionsAltogether, our findings suggest that recombinant EGFP can be used as a reducing and stabilizing agent for the preparation of biocompatible graphene. The novelty and originality of this work is that it describes a safe, simple, and environmentally friendly method for the production of graphene using recombinant enhanced green fluorescent protein. Furthermore, the synthesized graphene shows excellent biocompatibility with HEK cells; therefore, biologically synthesized graphene can be used for biomedical applications. To the best of our knowledge, this is the first and novel report describing the synthesis of graphene using recombinant EGFP.

Purification of recombinant EGFP by fusion with L2 (252–273) from ribosomal protein L2 using magnetic particles

A basic polypeptide L2 (252-273) derived from Escherichia coli ribosomal protein L2 was used as a purification tag. In order to develop faster, less expensive methods for expression and purification of proteins, the L2 (252-273)-small ubiquitin like modifier (SUMO) fusion expression system was constructed. We comparatively analyzed the adsorption properties of the deleted protein of L2 (L2 (252-273)) on diatomite and superparamagnetic carboxymethyl chitosan nanoparticles. The time required to reach adsorption equilibrium of L2 (252-273) fusion protein on diatomite was shorter than that of L2 (252-273) fusion protein on magnetic particles. The maximum adsorption capacity of L2 (252-273) fusion protein on magnetic particles was about 5 times larger than that of L2 (252-273) fusion protein on diatomite. SUMO was introduced as a specific protease cleavage site between the target protein and the purification tags. The enhanced green fluorescent protein (EGFP) as a model protein was fused with the L2 (252-273)-SUMO fusion protein and purified by a simple method which involves the electrostatic adsorption of L2 (252-273) fusion proteins on superparamagnetic carboxymethyl chitosan nanoparticles and the L2 (252-273)-SUMO fusion partner was removed based on the robust cleavage by the poly lysine tagged SUMO protease. The high purity of tag-free EGFP (>93%) was obtained. Our results preliminary proved that the system was an effective fusion expression system for the production of recombinant proteins in E. coli.

The construction and sub-cellular localization analysis of novel mycobacterial membrane-anchored expression vector

Objective To construct mycobacterial membrane-anchored expression vector and to analyze expression level and sub-cellualr localization of exogenous target protein. Methods Based on the mycobacterial intracellular expression vector pMFA42 which contained a strong promoter of pfurAma mutant, the signal sequence of Mycobacterium tuberculosis(Mtb) 19×103 lipoprotein (19SS) was synthesized and was then cloned into the downstream of pfurAma mutant to generate the mycobacterial membrane-anchored expression vector pMFA42M. The coding gene of enhanced green fluorescent protein(EGFP) was amplified by PCR, and then sub-cloned into these two vectors described above to construct recombinant EGFP fused and membrane-anchored strains, respectively. The coding genes of Mtb immuno-dominant antigens Ag85A and its chimera Ag856A2 were then sub-cloned intothe membrane-anchored construct pMFA42MG to produce recombinant Mtb antigen EGFP fused-expression strains. After that, expression levels and sub-cellualr localization of exogenous target protein were further analyzed by Western blot and flow cytometry sorting(FCS), and the fluorescence intensities of recombinant EGFP- expressed strains were observed in vitro directly and after transfection of murine macrophage cell line RAW264.7. Results The novel mycobacterial membrane-anchored expression vector was constructed successfully by introduction of signal sequence of Mtb 19×103 lipoprotein. Using of EGFP as model antigen, exogenous target protein was demonstrated to be expressed with high level and could be anchored into cell membrane of recombinant mycobaterial strains. Conclusion A novel mycobacterial membrane-anchored expression vector was constructed successfully to research recombinant BCG and functions of mycobacterial membrane proteins, and the constructed EGFP-expressed recombinant strains could also be used to research cytophagy in cell model and mycobacterial colony and translocation in animal immunization as model indicator bacteria. Key words: Mycobacteria; EGFP; Membrane-anchored expression vector; Sub-cellular localization

Hydrophobin signal sequence mediates efficient secretion of recombinant proteins in Pichia pastoris

Pichia pastoris is an important eukaryotic organism for the expression, processing, and secretion of recombinant proteins. Here, the secretion of enhanced green fluorescent protein (EGFP) in P. pastoris by using three novel secretion signals originating from the HFBI and HFBII class 2 hydrophobins of Trichoderma reesei was investigated. EGFP was fused to the carboxyl terminus of hydrophobin secretion signals and expressed under the control of the constitutive GAP promoter. In every case, recombinant EGFP entered the secretory pathway of P. pastoris. SDS-polyacrylamide gel electrophoresis, Western blot analysis of the cells' supernatant, and fluorescence measurements on single-cell level via flow cytometry confirmed the efficient secretion of EGFP mediated by the novel secretion sequences. In conclusion, the data clearly show that the secretion sequences derived from HFBI and HFBII of T. reesei have the potential to achieve an efficient secretion of heterologous proteins in P. pastoris. Due to the small size of the hydrophobin-derived secretion signals, their coding sequence can be easily introduced to the gene of interest by PCR.

Expression and stability of foreign tags inserted into nsp2 of porcine reproductive and respiratory syndrome virus (PRRSV)

The nonstructural protein 2 (nsp2) of porcine reproductive and respiratory syndrome virus (PRRSV) is the single largest protein produced during infection. The cDNA of the pCMV-129 infectious PRRSV clone was modified for accepting foreign tags by first creating unique Mlu I and SgrA I restrictions sites at nucleotide (nt) positions 3219 and 3614, respectively, within the C-terminal region of nsp2. cDNAs encoding oligo- and polypeptide tags, including FLAG, enhanced green fluorescent protein (EGFP) and luciferase were inserted into the newly created restriction sites. The results showed that only the EGFP-containing genomes were properly expressed and produced virus. EGFP fluorescence, but not EGFP immunoreactivity, was lost during passage of recombinant EGFP viruses in culture. Sequencing of a fluorescent-negative EGFP virus showed that the EGFP remained intact, except for the appearance of arginine to cysteine mutation at position 96, which may interfere with chromophore formation or function.

A functional chimaeric S-layer-enhanced green fluorescent protein to follow the uptake of S-layer-coated liposomes into eukaryotic cells.

The chimaeric gene encoding a C-terminally truncated form of the S-layer protein SbpA of Bacillus sphaericus CCM 2177 and the EGFP (enhanced green fluorescent protein) was ligated into plasmid pET28a and cloned and expressed in Escherichia coli. Just 1 h after induction of expression an intense EGFP fluorescence was detected in the cytoplasm of the host cells. Expression at 28 degrees C instead of 37 degrees C resulted in clearly increased fluorescence intensity, indicating that the folding process of the EGFP moiety was temperature sensitive. To maintain the EGFP fluorescence, isolation of the fusion protein from the host cells had to be performed in the presence of reducing agents. SDS/PAGE analysis, immunoblotting and N-terminal sequencing of the isolated and purified fusion protein confirmed the presence of both the S-layer protein and the EGFP moiety. The fusion protein had maintained the ability to self-assemble in suspension and to recrystallize on peptidoglycan-containing sacculi or on positively charged liposomes, as well as to fluoresce. Comparison of fluorescence excitation and emission spectra of recombinant EGFP and rSbpA(31-1068)/EGFP revealed identical maxima at 488 and 507 nm respectively. The uptake of liposomes coated with a fluorescent monomolecular protein lattice of rSbpA(31-1068)/EGFP into HeLa cells was studied by confocal laser-scanning microscopy. The major part of the liposomes was internalized within 2 h of incubation and entered the HeLa cells by endocytosis.

Concentrating rotavirus and recombinant enhanced green fluorescent protein fromE. coli using a temperature-sensitive hydrogel

Recombinant enhanced green fluorescent protein (EGFP) fromE. coli was concentrated 1.9 times by ultrafiltration using a temperature-sensitive hydrogel. Protein recovery and separation efficiency were 64% and 45%, respectively. Increased concentration of recombinant EGFP was confirmed by SDS-PAGE. Rotavirus was concentrated 3.2 times by ultrafiltration using a temperature-sensitive hydrogel, at 95% of virus recovery and 93% of separation efficiency. Hydrogel ultrafiltration appears to be an attractive alternative for the concentration of rotavirus and recombinant proteins fromE. coli.