Production Of Milligram Quantities Research Articles

Production and Purification of Antibodies in Chinese Hamster Ovary Cells.

Antibodies are versatile biological molecules with widespread applications in research and medicine. This protocol outlines the generation of monoclonal IgG antibodies from Chinese hamster ovary cells. It includes steps for cell maintenance, transient transfection, and antibody purification via protein A affinity chromatography. The methods described are intended for the production of milligram amounts of protein but can be adapted for most small- to mid-scale applications.

Facade-Based Bicelles as a New Tool for Production of Active Membrane Proteins in a Cell-Free System.

Integral membrane proteins are important components of a cell. Their structural and functional studies require production of milligram amounts of proteins, which nowadays is not a routine process. Cell-free protein synthesis is a prospective approach to resolve this task. However, there are few known membrane mimetics that can be used to synthesize active membrane proteins in high amounts. Here, we present the application of commercially available "Facade" detergents for the production of active rhodopsin. We show that the yield of active protein in lipid bicelles containing Facade-EM, Facade-TEM, and Facade-EPC is several times higher than in the case of conventional bicelles with CHAPS and DHPC and is comparable to the yield in the presence of lipid-protein nanodiscs. Moreover, the effects of the lipid-to-detergent ratio, concentration of detergent in the feeding mixture, and lipid composition of the bicelles on the total, soluble, and active protein yields are discussed. We show that Facade-based bicelles represent a prospective membrane mimetic, available for the production of membrane proteins in a cell-free system.

Production of Eukaryotic Glycoproteins for Structural and Functional Studies Using Expi293F Cells.

Milligram quantities of pure proteins are required for structural, functional, and pharmaceutical screening studies. These requirements can be challenging for a majority of important therapeutic targets that are secreted glycoproteins, receptors, membrane proteins, or large cytosolic complexes. Here, we present protocols for producing and purifying large amounts of secreted glycoproteins using the mammalian cell-based Expi293F system via large-scale transient transfection. This system can be easily adapted for the production of membrane proteins and large cytosolic complexes. The method can be utilized to quickly evaluate numerous expression constructs to identify optimal expressers. Use of mammalian cells ensures proper post-translational modifications, including disulfide bonds and glycosylation, that can be important for accurate functional studies. In addition, minor modifications can be introduced to produce labeled or deglycosylated proteins for structural studies by X-ray crystallography, nuclear magnetic resonance, or cryo-electron microscopy. © 2022 Wiley Periodicals LLC. Basic Protocol 1: Production of milligram quantities of plasmid DNA for large-scale transient transfection Basic Protocol 2: Large-scale culture and transient transfection of Expi293F cells Basic Protocol 3: Purification of hexahistidine-tagged proteins from medium.

Bacterial Production and Structural Study of Human Neuromodulator Lynx2

The human protein Lynx2 belongs to the Ly6/uPAR family of “three-finger” proteins and is associated with the cell membrane by the glycosylphosphatidylinositol (GPI) anchor. Lynx2 is expressed in the brain areas responsible for anxiety level control: prefrontal cortex, basolateral tonsil, hippocampus, and medial dorsal nucleus of the thalamus; it probably participates in anxiety regulation by interaction with α4β2 nicotinic acetylcholine receptor. Currently, the nature of the Lynx2 interaction with the receptor is unknown. We developed a bacterial expression system for production of a Lynx2 water-soluble domain (ws-Lynx2). The protein was obtained in the form of E. coli cytoplasmic inclusion bodies, with subsequent solubilization under denaturing conditions and renaturation. Production of milligram quantities of the 13С-15N-labeled variant of ws-Lynx2 made it possible to characterize the secondary structure of this protein by means of heteronuclear NMR spectroscopy. It was shown that ws-Lynx2 has structure typical for three-finger proteins from the Ly6/uPAR family with some unique features, such as helical elements in the first and third loops. Development of the effective recombinant production system opens up new horizons for further structural and functional studies of Lynx2.

Generation of Native, Untagged Huntingtin Exon1 Monomer and Fibrils Using a SUMO Fusion Strategy.

Huntington's Disease (HD) is an inherited fatal neurodegenerative disease caused by a CAG expansion (≥36) in the first exon of the HD gene, resulting in the expression of the Huntingtin protein (Htt) or N-terminal fragments thereof with an expanded polyglutamine (polyQ) stretch.The exon1 of the Huntingtin protein (Httex1) is the smallest Htt fragment that recapitulates many of the features of HD in cellular and animal models and is one of the most widely studied fragments of Htt. The small size of Httex1 makes it experimentally more amenable to biophysical characterization using standard and high-resolution techniques in comparison to longer fragments or full-length Htt. However, the high aggregation propensity of mutant Httex1 (mHttex1) with increased polyQ content (≥42) has made it difficult to develop efficient expression and purification systems to produce these proteins in sufficient quantities and make them accessible to scientists from different disciplines without the use of fusion proteins or other strategies that alter the native sequence of the protein. We present here a robust and optimized method for the production of milligram quantities of native, tag-free Httex1 based on the transient fusion of small ubiquitin related modifier (SUMO). The simplicity and efficiency of the strategy will eliminate the need to use non-native sequences of Httex1, thus making this protein more accessible to researchers and improving the reproducibility of experiments across different laboratories. We believe that these advances will also facilitate future studies aimed at elucidating the structure-function relationship of Htt as well as developing novel diagnostic tools and therapies to treat or slow the progression of HD.

Generation of Native, Untagged Huntingtin Exon1 Monomer and Fibrils Using a SUMO Fusion Strategy

Huntington's Disease (HD) is an inherited fatal neurodegenerative disease caused by a CAG expansion (≥36) in the first exon of the HD gene, resulting in the expression of the Huntingtin protein (Htt) or N-terminal fragments thereof with an expanded polyglutamine (polyQ) stretch. The exon1 of the Huntingtin protein (Httex1) is the smallest Htt fragment that recapitulates many of the features of HD in cellular and animal models and is one of the most widely studied fragments of Htt. The small size of Httex1 makes it experimentally more amenable to biophysical characterization using standard and high-resolution techniques in comparison to longer fragments or full-length Htt. However, the high aggregation propensity of mutant Httex1 (mHttex1) with increased polyQ content (≥42) has made it difficult to develop efficient expression and purification systems to produce these proteins in sufficient quantities and make them accessible to scientists from different disciplines without the use of fusion proteins or other strategies that alter the native sequence of the protein. We present here a robust and optimized method for the production of milligram quantities of native, tag-free Httex1 based on the transient fusion of small ubiquitin related modifier (SUMO). The simplicity and efficiency of the strategy will eliminate the need to use non-native sequences of Httex1, thus making this protein more accessible to researchers and improving the reproducibility of experiments across different laboratories. We believe that these advances will also facilitate future studies aimed at elucidating the structure-function relationship of Htt as well as developing novel diagnostic tools and therapies to treat or slow the progression of HD.

Recombinant Purification of the Periplasmic Portion of the LINC Complex.

Recombinant expression of proteins and their complexes is the routine laboratory procedure to generate pure reagents for biochemical and structural studies. Here we present the standard procedure developed in our lab for the production of milligram quantities of stoichiometric SUN-KASH complexes. The protocol was specifically developed for the purification of the periplasmic portion of LINC complexes.

Method for Efficient Refolding and Purification of Chemoreceptor Ligand Binding Domain.

Identification of natural ligands of chemoreceptors and structural studies aimed at elucidation of the molecular basis of the ligand specificity can be greatly facilitated by the production of milligram amounts of pure, folded ligand binding domains. Attempts to heterologously express periplasmic ligand binding domains of bacterial chemoreceptors in Escherichia coli (E. coli) often result in their targeting into inclusion bodies. Here, a method is presented for protein recovery from inclusion bodies, its refolding and purification, using the periplasmic dCACHE ligand binding domain of Campylobacter jejuni (C. jejuni) chemoreceptor Tlp3 as an example. The approach involves expression of the protein of interest with a cleavable His6-tag, isolation and urea-mediated solubilisation of inclusion bodies, protein refolding by urea depletion, and purification by means of affinity chromatography, followed by tag removal and size-exclusion chromatography. The circular dichroism spectroscopy is used to confirm the folded state of the pure protein. It has been demonstrated that this protocol is generally useful for production of milligram amounts of dCACHE periplasmic ligand binding domains of other bacterial chemoreceptors in a soluble and crystallisable form.

Recombinant production and structural studies of the human Lypd6 and Lypd6b proteins

Lypd6 and Lypd6b are human three-finger proteins expressed in various tissues and sharing a high degree of sequence homology (~54%). Unlike other members of the Ly6/uPAR family, both proteins additionally bear extended N- and С-terminal sequences flanking the LU-domain. The role of these sequences is unclear. It is known that Lypd6 can increase the amplitude of nicotine-induced calcium currents in mouse trigeminal ganglion neurons. The Danio rerio fish Lypd6 is involved in the regulation of the Wnt/β-cathenin signaling pathway and the knockdown of the lypd6 expression leads to the impairment of embryonic development. The Lypd6b expression in X. laevis oocytes increased the sensitivity of nicotinic acetylcholine receptors to acetylcholine and increased their desensitization rate. Molecular mechanisms of Lypd6 and Lypd6b action as well as their spatial structures remain unknown. In this work, the genes encoding water-soluble variants of human Lypd6 and Lypd6b lacking N-terminal sequences (rLypd6 and rLypd6b) and Lypd6 bearing the N-terminal sequence (N-rLypd6) were obtained and expressed. The proteins were expressed in cytoplasmic inclusion bodies followed by solubilization under denaturing conditions and renaturation. The renaturation conditions were screened to optimize recombinant protein yields. The analysis of NMR spectra of recombinant N-rLypd6, rLypd6, and rLypd6b demonstrated that N-rLypd6 may not have a structured form. The production of milligram quantities of isotope-labeled rLypd6 and rLypd6b analogues allowed characterization of the secondary structure of these proteins and study of their intramolecular dynamics. It was found that rLypd6 and rLypd6b have structural elements typical for the Ly6/uPAR family, although with some unique features, particularly, an additional disulfide bond in the third loop and helical regions in the first and third loops.

Wheat Germ Cell-Free Overexpression for the Production of Membrane Proteins.

Due to their hydrophobic nature, membrane proteins are notoriously difficult to express in classical cell-based protein expression systems. Often toxic, they also undergo degradation in cells or aggregate in inclusion bodies, making delicate issues further solubilization and renaturation. These are major bottlenecks in their structural and functional analysis. The wheat germ cell-free (WGE-CF) system offers an effective alternative not only to classical cell-based protein expression systems but also to other cell-free systems for the expression of membrane proteins. The WGE-CF indeed allows the production of milligram amounts of membrane proteins in a detergent-solubilized, homogenous, and active form. Here, we describe the method to produce a viral integral membrane protein, which is the non-structural protein 2 (NS2) of hepatitis C virus, in view of structural studies by solid-state NMR in a native-like lipid environment.

Escherichia coli-based production of recombinant ovine angiotensinogen and its characterization as a renin substrate.

BackgroundAngiotensinogen (ANG) is a macromolecular precursor of angiotensin, which regulates blood pressure and electrolyte balance. ANG is specifically cleaved by renin, an aspartic protease, to initiate the angiotensin-processing cascade. Ovine ANG (oANG) from sheep plasma has been shown to be a better substrate for human renin, and it has been used in clinical renin assays. To expand the availability of oANG, we aimed to produce milligram levels of recombinant oANG using an Escherichia coli expression system.ResultsWhen recombinant oANG was expressed from a T7 promoter in various E. coli strains at 37 °C, it accumulated in the insoluble fraction. However, by expressing oANG at 37 °C from a tac promoter, which has weaker transcriptional activity than a T7 promoter, we significantly elevated the ratio of soluble to insoluble recombinant oANG. Using a novel culturing system and auto-induction culture medium, we purified tac-expressed recombinant oANG to homogeneity, with a yield of 4.0 mg per liter of culture. Based on size-exclusion gel filtration analysis and dynamic light scattering analysis, the resulting purified oANG is a monomer in solution. The circular dichroism spectrum of E. coli-expressed recombinant oANG was similar to that of oANG expressed in CHO cells. Differential scanning fluorimetry showed that both preparations undergo a two-state transition during thermal denaturation, and the melting temperatures of recombinant oANG expressed in E. coli and CHO cells were 49.4 ± 0.16 °C and 51.6 ± 0.19 °C, respectively. The Km values of both oANG preparations were similar; the kcat value of E. coli-expressed recombinant oANG was slightly higher than that of CHO-expressed oANG.ConclusionsRecombinant oANG expressed in E. coli functions as a human renin substrate. This study presents an E. coli-based system for the rapid production of milligram quantities of a human renin substrate, which will be useful for both fundamental and clinical studies on renin and hypertension.Electronic supplementary materialThe online version of this article (doi:10.1186/s12896-016-0265-x) contains supplementary material, which is available to authorized users.

A Streamlined, Automated Protocol for the Production of Milligram Quantities of Untagged Recombinant Rat Lactate Dehydrogenase A Using ÄKTAxpressTM.

We developed an efficient, automated 2-step purification protocol for the production of milligram quantities of untagged recombinant rat lactate dehydrogenase A (rLDHA) from E. coli, using the ÄKTAxpress™ chromatography system. Cation exchange followed by size exclusion results in average final purity in excess of 93% and yields ~ 14 milligrams per 50 ml of original cell culture in EnPresso B media, in under 8 hrs, including all primary sample processing and column equilibration steps. The protein is highly active and coherent biophysically and a viable alternative to the more problematic human homolog for structural and ligand-binding studies; an apo structure of untagged rLDHA was solved to a resolution 2.29 Å (PDB ID 5ES3). Our automated methodology uses generic commercially available pre-packed columns and simple buffers, and represents a robust standard method for the production of milligram amounts of untagged rLDHA, facilitating a novel fragment screening approach for new inhibitors.

Efficient segmental isotope labeling of multi-domain proteins using Sortase A.

NMR studies of multi-domain protein complexes provide unique insight into their molecular interactions and dynamics in solution. For large proteins domain-selective isotope labeling is desired to reduce signal overlap, but available methods require extensive optimization and often give poor ligation yields. We present an optimized strategy for segmental labeling of multi-domain proteins using the S. aureus transpeptidase Sortase A. Critical improvements compared to existing protocols are (1) the efficient removal of cleaved peptide fragments by centrifugal filtration and (2) a strategic design of cleavable and non-cleavable affinity tags for purification. Our approach enables routine production of milligram amounts of purified segmentally labeled protein for NMR and other biophysical studies.

Method to increase the yield of eukaryotic membrane protein expression in Saccharomyces cerevisiae for structural and functional studies.

Despite recent successes in the structure determination of eukaryotic membrane proteins, the total number of structures of these important proteins is severely underrepresented in the Protein Data Bank. Although prokaryotic homologues provide valuable mechanistic insight, they often lack crucial details, such as post-translational modification and additional intra or extracellular domains that are important for understanding the function and regulation of these proteins in eukaryotic cells. The production of milligram quantities of recombinant protein is still a serious obstacle to the structural and functional characterization of these proteins. Here, we report a modification to a previously described over expression system using the simple eukaryote Saccharomyces cerevisiae that can increase overall protein yield and improve downstream purification procedures. Using a metabolic marker under the control of a truncated promoter, we show that expression levels for several membrane transporters are increased fourfold. We further demonstrate that the increase in expression for our test proteins resulted in a concomitant increase in functional protein. Using this system, we were able to increase the expression level of a plant transporter, NRT1.1, which was a key factor in its structural and functional characterization.

Expression and purification of soluble recombinant full length HIV-1 Pr55Gag protein in Escherichia coli

The HIV-1 Gag precursor protein, Pr55Gag, is a multi-domain polyprotein that drives HIV-1 assembly. The morphological features of HIV-1 suggested Pr55Gag assumes a variety of different conformations during virion assembly and maturation, yet structural determination of HIV-1 Pr55Gag has not been possible due to an inability to express and to isolate large amounts of full-length recombinant Pr55Gag for biophysical and biochemical analyses. This challenge is further complicated by HIV-1 Gag’s natural propensity to multimerize for the formation of viral particle (with ∼2500 Gag molecules per virion), and this has led Pr55Gag to aggregate and be expressed as inclusion bodies in a number of in vitro protein expression systems. This study reported the production of a recombinant form of HIV-1 Pr55Gag using a bacterial heterologous expression system. Recombinant HIV-1 Pr55Gag was expressed with a C-terminal His×6 tag, and purified using a combination of immobilized metal affinity chromatography and size exclusion chromatography. This procedure resulted in the production of milligram quantities of high purity HIV-1 Pr55Gag that has a mobility that resembles a trimer in solution using size exclusion chromatography analysis. The high quantity and purity of the full length HIV Gag will be suitable for structural and functional studies to further understand the process of viral assembly, maturation and the development of inhibitors to interfere with the process.

The Use of Transient Expression Systems for the Rapid Production of Virus-like Particles in Plants

Advances in transient expression technologies have allowed the production of milligram quantities of proteins within a matter of days using only small amounts (tens of grams) of plant tissue. Among the proteins that have been produced using this approach are the structural proteins of viruses which are capable of forming virus-like particles (VLPs). As such particulate structures are potent stimulators of the immune system, they are excellent vaccine candidates both in their own right and as carriers of additional immunogenic sequences. VLPs of varying complexity derived from a variety of animal viruses have been successfully transiently expressed in plants and their immunological properties assessed. Generally, the plant-produced VLPs were found to have the expected antigenicity and immunogenicity. In several cases, including an M2e-based influenza vaccine candidate, the plant-expressed VLPs have been shown to be capable of stimulating protective immunity. These findings raise the prospect that low-cost plant-produced vaccines could be developed for both veterinary and human use.

Human neuromodulator SLURP-1: Bacterial expression, binding to muscle-type nicotinic acetylcholine receptor, secondary structure, and conformational heterogeneity in solution

Human protein SLURP-1 is an endogenous neuromodulator belonging to the Ly-6/uPAR family and acting on nicotinic acetylcholine receptors. In the present work, the gene of SLURP-1 was expressed in E. coli. The bacterial systems engineered for SLURP-1 expression as fused with thioredoxin and secretion with leader peptide STII failed in the production of milligram quantities of the protein. The SLURP-1 was produced with high-yield in the form of inclusion bodies, and different methods of the protein refolding were tested. Milligram quantities of recombinant SLURP-1 and its (15)N-labeled analog were obtained. The recombinant SLURP-1 competed with (125)I-α-bungarotoxin for binding to muscle-type Torpedo californica nAChR at micromolar concentrations, indicating a partial overlap in the binding sites for SLURP-1 and α-neurotoxins on the receptor surface. NMR study revealed conformational heterogeneity of SLURP-1 in aqueous solution, which was associated with cis-trans isomerization of the Tyr39-Pro40 peptide bond. The two structural forms of the protein have almost equal population in aqueous solution, and exchange process between them takes place with characteristic time of about 4ms. Almost complete (1)H and (15)N resonance assignment was obtained for both structural forms of SLURP-1. The secondary structure of SLURP-1 involves two antiparallel β-sheets formed from five β-strands and closely resembles those of three-finger snake neurotoxins.

Bacterial expression and purification of the amyloidogenic peptide PAPf39 for multidimensional NMR spectroscopy

PAPf39 is a 39 residue peptide fragment from human prostatic acidic phosphatase that forms amyloid fibrils in semen. These fibrils have been implicated in facilitating HIV transmission. To enable structural studies of PAPf39 by NMR spectroscopy, efficient methods allowing the production of milligram quantities of isotopically labeled peptide are essential. Here, we report the high-yield expression and purification of uniformly 13C- and 15N-labeled PAPf39 peptide, through expression as a fusion to ubiquitin at the N-terminus and an intein at the C-terminus. This allows the study of the PAPf39 monomer conformational ensemble by NMR spectroscopy. To this end, we performed the NMR chemical shift assignment of the PAPf39 peptide in the monomeric state at low pH.

Cell‐free expression of disulfide‐containing eukaryotic proteins for structural biology

We describe Escherichia coli based cell-free production of milligram quantities of eukaryotic proteins containing native disulfide bonds. Using a previously described expression system, we systematically investigated the influence of redox potential variation in the reaction mixture and the impact of adding disulfide bond catalysts on soluble protein production. It is then shown that the optimized reaction conditions for native disulfide bond formation can be combined with the use of N-terminal fusion constructs with the GB1 domain for increased expression yields. The resulting cell-free system is suitable for stable-isotope labeling and does not require chemical pretreatment of the cell extract to stabilize the redox potential. For the human doppel protein, the mouse doppel protein and mouse interleukin-22 we obtained 0.3-0.7 mg of purified native protein per milliliter of reaction mixture. Formation of disulfide bonds was validated using the Ellman assay, and native folding of the three proteins was monitored by NMR and CD spectroscopy.

Bacterial Synthesis and Purification of Normal and Mutant Forms of Human FGFR3 Transmembrane Segment

The fibroblast growth factor receptor 3 (FGFR3) is a protein belonging to the family of receptor tyrosine kinases. FGFR3 plays an important role in human skeletal development. Mutations in this protein, including Gly380Arg or Ala391Glu substitutions in the transmembrane (TM) region, can cause different disorders in bone development. The determination of the spatial structure of the FGFR3 TM domain in a normal protein and in a protein with single Gly380Arg and Ala391Glu mutations is essential in order to understand the mechanisms that control dimerization and signal transduction by receptor tyrosine kinases. The effective system of expression of eukaryotic genes in bacteria and the purification protocol for the production of milligram amounts of both normal TM fragments of FGFR3 and those with single pathogenic mutations Gly380Arg and Ala391Glu, as well as their(15)N- and [(15)N,(13)C]-isotope-labelled derivatives, were described. Each peptide was produced inEscherichia coliBL21(DE3)pLysS cells as a C-terminal extension of thioredoxin A. The purification protocol involved immobilized metal affinity chromatography and cation- and anion-exchange chromatography, as well as the fusion protein cleavage with the light subunit of human enterokinase. The efficiency of the incorporation of target peptides into DPC/SDS and DPC/DPG micelles was confirmed using NMR spectroscopy. The described methodology of production of the native FGFR3 TM domain in norma and with single Gly380Arg and Ala391Glu mutations enables one to study their spatial structure using high-resolution heteronuclear NMR spectroscopy.