Expression and purification of recombinant neurotensin in Escherichia coli

High yield expression and purification of full-length Neurotensin with pyroglutamate modification

Neurotensin (NT) is a 13-residue endogenous peptide found in mammals, with neurotransmission and hormonal roles in the central nervous system and gastrointestinal tract, respectively. The first residue of NT is a pyroglutamate (pGlu) that makes the expression and purification of large amounts of NT with native modification challenging. Here, we describe a simple and efficient procedure for expression and purification of large amounts of NT based on using the small ubiquitin-like modifier (SUMO) as a fusion partner and subsequent enzymatic conversion of the N-terminal glutamine to pGlu. Yields of 13 mg/L and 8 mg/L of pure peptide were obtained from expression in rich and minimal media, respectively. The method is adaptable to expression and purification of proteins and peptides with pGlu modification in a wide range of eukaryotic and prokaryotic expression hosts.

Neuropeptides in Cancer: Friend and Foe?

Neuropeptides are small regulatory molecules found throughout the body, most notably in the nervous, cardiovascular, and gastrointestinal systems. They serve as neurotransmitters or hormones in the regulation of diverse physiological processes. Cancer cells escape normal growth control mechanisms by altering their expression of growth factors, receptors, or intracellular signals, and neuropeptides have recently been recognized as mitogens in cancer growth and development. Many neuropeptides and their receptors exist in multiple subtypes, coupling with different downstream signaling pathways and playing distinct roles in cancer progression. The consideration of neuropeptide/receptor systems as anticancer targets is already leading to new biological and diagnostic knowledge that has the potential to enhance the understanding and treatment of cancer. In this review, recent discoveries regarding neuropeptides in a wide range of cancers, emphasizing their mechanisms of action, signaling cascades, regulation, and therapeutic potential, are discussed. Current technologies used to manipulate and analyze neuropeptides/receptors are described. Applications of neuropeptide analogs and their receptor inhibitors in translational studies and radio-oncology are rapidly increasing, and the possibility for their integration into therapeutic trials and clinical treatment appears promising.

Bacterial fermentation and isotope labelling optimized for amyloidogenic proteins

We developed a cost sensitive isotope labelling procedure using a fed-batch fermentation method and tested its efficiency producing the 15 N-, 13 C- and 15 N/13 C-labelled variants of an amyloidogenic miniprotein (E5: EEEAVRLYIQWLKEGGPSSGRPPPS). E5 is a surface active protein, which forms amyloids in solution. Here, we confirm, using both PM-IRRAS and AFM measurements, that the air-water interface triggers structural rearrangement and promotes the amyloid formation of E5, and thus it is a suitable test protein to work out efficient isotope labelling schemes even for such difficult sequences. E. coli cells expressing the recombinant, ubiquitin-fused miniprotein were grown in minimal media containing either unlabelled nutrients, or 15 N-NH4 Cl and/or 13 C-D-Glc. The consumption rates of NH4 Cl and D-Glc were quantitatively monitored during fermentation and their ratio was established to be 1:5 (for NH4 Cl: D-Glc). One- and two-step feeding schemes were custom-optimized to enhance isotope incorporation expressing five different E5 miniprotein variants. With the currently optimized protocols we could achieve a 1.5- to 5-fold increase of yields of several miniproteins coupled to a similar magnitude of cost reduction as compared to flask labelling protocols.

How to investigate interactions between membrane proteins and ligands by solid-state NMR

Solid-state NMR is an established method for biophysical studies of membrane proteins within the lipid bilayers and an emerging technique for structural biology in general. In particular magic angle sample spinning has been found to be very useful for the investigation of large membrane proteins and their interaction with small molecules within the lipid bilayer. Using a number of examples, we illustrate and discuss in this chapter, which information can be gained and which experimental parameters need to be considered when planning such experiments. We focus especially on the interaction of diffusive ligands with membrane proteins.

Molecular cloning and functional characterization of a mouse ccl6 analog gene in the rat

Suppression subtractive hybridization was used to analyze differential expression of genes in rat peritoneal macrophages after granulocyte macrophage colony-stimulating factor treatment. We identified and cloned the mouse C10 analog gene in the rat, and named it as ccl6. The full-length cDNA of rat ccl6 was 467 bp, which contains a single-open reading frame and encodes 116 amino acid residues. Compared with other C-C chemokines, the rat ccl6 gene had an unusual four-exon genome structure instead of the typical three exons, it had the highest homology with murine ccl6. The rat ccl6 gene was localized on chromosome 10, where most of the C-C chemokine superfamily members are located. The recombinant rat C-C chemokine ligand 6 (CCL6) protein was expressed by the pGEX4T-1 plasmid in Escherichia coli BL21. The purified recombinant protein had bioactivity similar to that of mouse CCL6, which is a chemoattractant for macrophages and lymphocytes, but not for neutrophils.

Expression and purification of a recombinant amyloidogenic peptide from transthyretin for solid-state NMR spectroscopy

We describe the expression and purification of a model amyloidogenic peptide comprising residues 105-115 of human transthyretin (TTR105-115). Recombinant TTR105-115, which does not contain any non-native residues, was prepared as part of a fusion protein construct with a highly soluble B1 immunoglobulin binding domain of protein G (GB1), with typical yields of approximately 4 mg/L of uniformly (13)C,(15)N-enriched HPLC-purified peptide per liter of minimal media culture. Amyloid fibrils formed by recombinant TTR105-115 were characterized by transmission electron microscopy and solid-state NMR spectroscopy, and found to be comparable to synthetic TTR105-115 fibrils. These results establish recombinant TTR105-115 as a valuable model system for the development of new solid-state NMR techniques for the atomic-level characterization of amyloid architecture.

Expression and purification of a recombinant peptide from the Alzheimer's beta-amyloid protein for solid-state NMR

Fibrillar protein aggregates contribute to the pathology of a number of disease states. To facilitate structural studies of these amyloid fibrils by solid-state NMR, efficient methods for the production of milligram quantities of isotopically labeled peptide are necessary. Bacterial expression of recombinant amyloid proteins and peptides allows uniform isotopic labeling, as well as other patterns of isotope incorporation. However, large-scale production of recombinant amyloidogenic peptides has proven particularly difficult, due to their inherent propensity for aggregation and the associated toxicity of fibrillar material. Yields of recombinant protein are further reduced by the small molecular weights of short amyloidogenic fragments. Here, we report high-yield expression and purification of a peptide comprising residues 11-26 of the Alzheimer's beta-amyloid protein (Abeta(11-26)), with homoserine lactone replacing serine at residue 26. Expression in inclusion bodies as a ketosteroid isomerase fusion protein and subsequent purification under denaturing conditions allows production of milligram quantities of uniformly labeled (13)C- and (15)N-labeled peptide, which forms amyloid fibrils suitable for solid-state NMR spectroscopy. Initial structural data obtained by atomic force microscopy, electron microscopy, and solid-state NMR measurements of Abeta(11-26) fibrils are also presented.

Heterologous expression, characterization and structural studies of a hydrophobic peptide from the HIV-1 p24 protein

Proteins from the inner core of HIV-1, such as the capsid protein (p24), are involved in crucial processes during the virus life cycle. The p24 protein plays an active structural role in the Gag protein and in its mature form. This work describes the production of a peptide derived from the p24 C-terminal, TLRAEQASQEVKNWMTETLLVQNA, using recombinant technology. This region (p24-3) is involved in interfaces during the p24 dimerization, which occurs during capsid assembly. The p24-3 sequence was obtained by a synthetic gene strategy and inserted into the pET 32a expression vector to produce soluble fusion protein in Escherichia coli BL21(DE3). This strategy leads to an incorporation of three amino acid residues (AMA) in the N-terminal of the native sequence to form the recombinant p24-3 (rp24-3). The rp24-3 was purified by reverse phase chromatography to homogeneity, as inferred by mass spectrometry and protein sequence analysis. Structural studies using circular dichroism and steady-state fluorescence showed that the rp24-3 is structured by helical and beta elements. As a function of its hydrophobic character it can self-associate forming oligomers. We present in this paper the first development of a suitable expression system for rp24-3, which provides high amounts of the peptide. This strategy will allow the development of new antiviral (HIV) agents.

Bioprocess-centered molecular design (BMD) for the efficient production of an interfacially active peptide

The efficient expression and purification of an interfacially active peptide (mLac21) was achieved by using bioprocess-centered molecular design (BMD), wherein key bioprocess considerations are addressed during the initial molecular biology work. The 21 amino acid mLac21 peptide sequence is derived from the lac repressor protein and is shown to have high affinity for the oil-water interface, causing a substantial reduction in interfacial tension following adsorption. The DNA coding for the peptide sequence was cloned into a modified pET-31(b) vector to permit the expression of mLac21 as a fusion to ketosteroid isomerase (KSI). Rational iterative molecular design, taking into account the need for a scaleable bioprocess flowsheet, led to a simple and efficient bioprocess yielding mLac21 at 86% purity following ion exchange chromatography (and >98% following chromatographic polishing). This case study demonstrates that it is possible to produce acceptably pure peptide for potential commodity applications using common scaleable bioprocess unit operations. Moreover, it is shown that BMD is a powerful strategy that can be deployed to reduce bioseparation complexity.

Expression and purification of the anticomplementary peptide Sh-CRIT-ed1 (formerly Sh-TOR-ed1) as a tetramultimer in Escherichia coli

Many complement inhibitors found in plants and other organisms have been recognized as an antiinflammatory drug. Sh-CRIT-ed1 is a complement inhibitory peptide, present on the Schistosoma parasite surface. In the present study, we expressed chemically synthesized oligonucleotides encoding Sh-CRIT-ed1 with an additional hexahistidine codon at the C-terminus and purified in Escherichia coli BL21. The cloned gene, which was multimerized four times in pBlue-script II KS (+) at the isoschizomer sites (BamHI, BglII), was named Sh4, and expressed in E. coli BL21 harboring pGEX-KG. The fusion protein (GST-Sh4) was purified with high yield successively by affinity chromatographies of glutathione-Sepharose 4B and Ni-NTA-agarose. Recombinant Sh-CRIT-ed1 was obtained readily by thrombin digestion and CNBr cleavage of GST-Sh4, and the yield was 9.03 mg from 1-liter culture of E. coli BL21 harboring pGEX-Sh4. The recombinant Sh-CRIT-ed1 showed strong anticomplementary activity (IC(50) = 6.02 microM) by complement haemolysis assay.

Applications of novel affinity cassette methods: use of peptide fusion handles for the purification of recombinant proteins

In this article, recent progress related to the use of different types of polypeptide fusion handles or 'tags' for the purification of recombinant proteins are critically discussed. In addition, novel aspects of the molecular cassette concept are elaborated, together with areas of potential application of these fundamental principles in molecular recognition. As evident from this review, the use of these concepts provides a powerful strategy for the high throughput isolation and purification of recombinant proteins and their derived domains, generated from functional genomic or zeomic studies, as part of the bioprocess technology leading to their commercial development, and in the study of molecular recognition phenomena per se. In addition, similar concepts can be exploited for high sensitivity analysis and detection, for the characterisation of protein bait/prey interactions at the molecular level, and for the immobilisation and directed orientation of proteins for use as biocatalysts/biosensors.

SwellGel: an affinity chromatography technology for high-capacity and high-throughput purification of recombinant-tagged proteins

The revolution in genomics and proteomics is having a profound impact on drug discovery. Today's protein scientist demands a faster, easier, more reliable way to purify proteins. A high capacity, high-throughput new technology has been developed in Perbio Sciences for affinity protein purification. This technology utilizes selected chromatography media that are dehydrated to form uniform aggregates. The SwellGel aggregates will instantly rehydrate upon addition of the protein sample, allowing purification and direct performance of multiple assays in a variety of formats. SwellGel technology has greater stability and is easier to handle than standard wet chromatography resins. The microplate format of this technology provides high-capacity, high-throughput features, recovering milligram quantities of protein suitable for high-throughput screening or biophysical/structural studies. Data will be presented applying SwellGel technology to recombinant 6x His-tagged protein and glutathione-S-transferase (GST) fusion protein purification.