Integrated production of human insulin and its C-peptide

New and efficient purification process for recombinant human insulin produced in Escherichia coli

A new and efficient purification process for recombinant human insulin production was developed by exploring new resins and optimizing purification steps from E. coli inclusion body washing to insulin polishing. A combined additives inclusion body wash protocol drastically improved efficiency in clarifying ZZ-proinsulin samples. ZZ-proinsulin recovery increased three-fold under optimized solubilization and sulfitolysis incubation temperature and duration. Desalting with Bio-Gel P4 and P6 resulted in higher sample loading and product recovery compared to conventional resins. A higher recovery (96%) and purity (81%) of ZZ-proinsulin were achievable with the Nuvia S cation exchanger for proinsulin purification compared to a reported process using expensive affinity chromatography resin. As the first step for insulin purification, process scale-up is more economical and practical when Nuvia HR-S cation exchanger was used instead of commonly used reversed-phase chromatography. Nuvia HR-S was highly effective in removing ZZ fusion protein (90% removal) after enzymatic cleavage, although ZZ fusion protein has a very close theoretical pI to human insulin, which was supposedly challenging to be removed by cation exchange chromatography. Also, insulin can be eluted at a lower ethanol % using Nuvia HR-S compared to other reported processes and is thus more environmentally sustainable. Recombinant human insulin was obtained with over 98% purity in just a single reversed-phase polishing step, which is comparable to the reference standard. The process workflow presented here can be potentially applied for the development of purification workflow for insulin analogs or other peptide products derived from E. coli inclusion body.Key points• Drastic efficiency improvement for inclusion body wash with combined additives.• High recovery of proinsulin purification with high capacity cation exchange resin.• Effective removal of fusion tag at lower ethanol % with high-resolution resin.

Downstream processing of recombinant human insulin and its analogues production from E. coli inclusion bodies

The Global Diabetes Compact was launched by the World Health Organization in April 2021 with one of its important goals to increase the accessibility and affordability of life-saving medicine-insulin. The rising prevalence of diabetes worldwide is bound to escalate the demand for recombinant insulin therapeutics, and currently, the majority of recombinant insulin therapeutics are produced from E. coli inclusion bodies. Here, a comprehensive review of downstream processing of recombinant human insulin/analogue production from E. coli inclusion bodies is presented. All the critical aspects of downstream processing, starting from proinsulin recovery from inclusion bodies, inclusion body washing, inclusion body solubilization and oxidative sulfitolysis, cyanogen bromide cleavage, buffer exchange, purification by chromatography, pH precipitation and zinc crystallization methods, proinsulin refolding, enzymatic cleavage, and formulation, are explained in this review. Pertinent examples are summarized and the practical aspects of integrating every procedure into a multimodal purification scheme are critically discussed. In the face of increasing global demand for insulin product, there is a pressing need to develop a more efficient and economical production process. The information presented would be insightful to all the manufacturers and stakeholders for the production of human insulins, insulin analogues or biosimilars, as they strive to make further progresses in therapeutic recombinant insulin development and production.

High-Performance Reversed-Phase Flash Chromatography Purification of Peptides and Chemically Modified Insulins

Preparative reversed-phase HPLC is the established method for the purification of peptides, but has significant limitations. We systematically investigated the use of high-performance reversed-phase flash chromatography (HPFC) to rapidly purify laboratory-scale quantities of crude, synthetic peptides and chemically modified insulins. We demonstrated these methods for a diverse set of peptides, including short, medium, and long peptides. Depending on the purity profile of the peptide, HPFC can be used either as the sole purification method, or as a pre-purification method prior to final HPLC purification. Furthermore, HPFC is suitable for the purification of peptides that are not fully in solution. We provide guidelines for the HPFC of synthetic peptides and small proteins, including the choice of columns, eluents, and gradients. We believe that HPFC is a valuable alternative to HPLC purification of peptides and small proteins.

Insulin fibrillation: toward strategies for attenuating the process

The environmental factors affecting the rate of insulin fibrillation. The factors are representative.

Applications of in Silico Methods for Design and Development of Drugs Targeting Protein-Protein Interactions

BACKGROUND

Identification of Protein-Protein Interactions (PPIs) is a major challenge in modern molecular biology and biochemistry research, due to the unquestionable role of proteins in cells, biological process and pathological states. Over the past decade, the PPIs have evolved from being considered a highly challenging field of research to being investigated and examined as targets for pharmacological intervention.

OBJECTIVE

Comprehension of protein interactions is crucial to known how proteins come together to build signalling pathways, to carry out their functions, or to cause diseases, when deregulated. Multiplicity and great amount of PPIs structures offer a huge number of new and potential targets for the treatment of different diseases.

METHODS

Computational techniques are becoming predominant in PPIs studies for their effectiveness, flexibility, accuracy and cost. As a matter of fact, there are effective in silico approaches which are able to identify PPIs and PPI site. Such methods for computational target prediction have been developed through molecular descriptors and data-mining procedures.

RESULTS

In this review, we present different types of interactions between protein-protein and the application of in silico methods for design and development of drugs targeting PPIs. We described computational approaches for the identification of possible targets on protein surface and to detect of stimulator/ inhibitor molecules.

CONCLUSION

A deeper study of the most recent bioinformatics methodologies for PPIs studies is vital for a better understanding of protein complexes and for discover new potential PPI modulators in therapeutic intervention.

Functionality of an absolutely conserved glycine residue in the chimeric relaxin family peptide R3/I5

The insulin superfamily is a group of homologous proteins that are further divided into the insulin family and relaxin family according to their distinct receptors. All insulin superfamily members contain three absolutely conserved disulfide linkages and a nonchiral Gly residue immediately following the first B-chain cysteine. The functionality of this conserved Gly residue in the insulin family has been studied by replacing it with natural L-amino acids or the corresponding unnatural D-amino acids. However, such analysis has not been conducted on relaxin family members. In the present study, we conducted chiral mutagenesis on the conserved B11Gly of the chimeric relaxin family peptide R3/I5, which is an efficient agonist for receptor RXFP3 and RXFP4. Similar to the effects on insulin family foldability, L-Ala or L-Ser substitution completely abolished the in vitro refolding of a recombinant R3/I5 precursor; whereas, D-Ala or D-Ser substitution had no detrimental effect on refolding of a semi-synthetic R3/I5 precursor, suggesting that the conserved Gly residue controls the foldability of relaxin family members. In contrast to the effect on insulin family activity, D-Ala or D-Ser replacement had no detrimental effect on the binding and activation potencies of the mature R3/I5 towards both RXFP3 and RXFP4, suggesting that the conserved Gly residue is irrelevant to the relaxin family's activity. The present study revealed functionality of the conserved B-chain Gly residue for a relaxin family peptide for the first time, providing an overview of its contribution to foldability and activity of the insulin superfamily.

Human αB-crystallin as fusion protein and molecular chaperone increases the expression and folding efficiency of recombinant insulin

Low expression and instability are significant challenges in the recombinant production of therapeutic peptides. The current study introduces a novel expression and purification system for human insulin production using the molecular chaperone αB-crystallin (αB-Cry) as a fusion partner protein. Insulin is composed of A- and B-chain containing three disulfide bonds (one intarchain and two interchains). We have constructed two plasmids harboring the A- or B-chain of insulin joined with human αB-Cry. This system is suitable for cloning of the genes and for directing the synthesis of large amounts of the fusion proteins αB-Cry/A-chain (αB-AC) and αB-Cry/B-chain (αB-BC). The construction of vectors, their efficient expression in Escherichia coli and simple purification of the fusion proteins and two insulin chains are described. A large amount of the recombinant fusion proteins with high purity was obtained by applying a single step anion exchange chromatography or metal chelate affinity. The insulin A- and B-chain were released from the fusion proteins using cyanogen bromide cleavage. The insulin peptides were obtained with an appreciable yield and high purity using one-step gel filtration chromatography. To increase efficiency of chain combination to produce insulin, αB-Cry was used under oxidative conditions. The purification of natively folded insulin was performed by phenyl sepharose hydrophobic interaction chromatography. Finally, using an insulin tolerance test in mice and various biophysical methods, the structure and function of purified human recombinant insulin was compared with authentic insulin, to verify folding of insulin to its native state. Overall, the novel expression system using αB-Cry is highly demanding for producing human insulin and functional protein. The procedure for αB-Cry-mediated insulin folding could be also applicable for the large-scale production of this highly important therapeutic peptide hormone.

Wanted: more monitoring and control during inclusion body processing

Inclusion bodies (IBs) are insoluble aggregates of misfolded protein in Escherichia coli. Against the outdated belief that the production of IBs should be avoided during recombinant protein production, quite a number of recombinant products are currently produced as IBs, which are then processed to give correctly folded and soluble product. However, this processing is quite cumbersome comprising IB wash, IB solubilization and refolding. To date, IB processing often happens rather uncontrolled and relies on empiricism rather than sound process understanding. In this mini review we describe current efforts to introduce more monitoring and control in IB processes, focusing on the refolding step, and thus generate process understanding and knowledge.

Structural Analysis of Recombinant Human Preproinsulins by Structure Prediction, Molecular Dynamics, and Protein-Protein Docking

More effective production of human insulin is important, because insulin is the main medication that is used to treat multiple types of diabetes and because many people are suffering from diabetes. The current system of insulin production is based on recombinant DNA technology, and the expression vector is composed of a preproinsulin sequence that is a fused form of an artificial leader peptide and the native proinsulin. It has been reported that the sequence of the leader peptide affects the production of insulin. To analyze how the leader peptide affects the maturation of insulin structurally, we adapted several in silico simulations using 13 artificial proinsulin sequences. Three-dimensional structures of models were predicted and compared. Although their sequences had few differences, the predicted structures were somewhat different. The structures were refined by molecular dynamics simulation, and the energy of each model was estimated. Then, protein-protein docking between the models and trypsin was carried out to compare how efficiently the protease could access the cleavage sites of the proinsulin models. The results showed some concordance with experimental results that have been reported; so, we expect our analysis will be used to predict the optimized sequence of artificial proinsulin for more effective production.

Site-Specific Disulfide Crosslinked Nucleosomes with Enhanced Stability

We engineered nucleosome core particles (NCPs) with two site-specific cysteine crosslinks that increase the stability of the particle. The first disulfide was introduced between the two copies of H2A via an H2A-N38C point mutation, effectively crosslinking the two H2A/H2B heterodimers together to stabilize the histone octamer against H2A/H2B dimer dissociation. The second crosslink was engineered between an R40C point mutation on the N-terminal tail of H3 and the NCP DNA ends by the introduction of a convertible nucleotide. This crosslink maintains the nucleosome DNA in a fixed translational setting relative to the histone octamer and prevents dilution-driven dissociation. The X-ray crystal structures of NCPs containing the disulfides in isolation and in combination were determined. Both disulfides stabilize the structure of the NCP without disturbing the overall structure. Nucleosomes containing these modifications will be advantageous for biochemical and structural studies as a consequence of their greater resistance to dissociation during high dilution in purification, elevated salt for crystallization and vitrification for cryogenic electron microscopy.

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Crosslinked nucleosome core particles have increased stability against H2A/H2B dimer loss and DNA dissociation.

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A site-specific disulfide crosslink was introduced between the two copies of H2A in the histone octamer to stabilize its quaternary structure.

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Site-specific disulfide crosslinks were introduced between histone H3 and DNA within the nucleosome core particle.

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Three X-ray crystal structures of crosslinked nucleosome core particles were determined at high resolution.

Protein fusion tags for efficient expression and purification of recombinant proteins in the periplasmic space of E. coli

Disulfide bonds occurred in majority of secreted protein. Formation of correct disulfide bonds are must for achieving native conformation, solubility and activity. Production of recombinant proteins containing disulfide bond for therapeutic, diagnostic and various other purposes is a challenging task of research. Production of such proteins in the reducing cytosolic compartment of E. coli usually ends up in inclusion bodies formation. Refolding of inclusion bodies can be difficult, time and labor consuming and uneconomical. Translocation of these proteins into the oxidative periplasmic compartment provides correct environment to undergo proper disulfide bonds formation and thus achieving native conformation. However, not all proteins can be efficiently translocated to the periplasm with the help of bacterial signal peptides. Therefore, fusion to a small well-folded and stable periplasmic protein is more promising for periplasmic production of disulfide bonded proteins. In the past decades, several full-length proteins or domains were used for enhancing translocation and solubility. Here, protein fusion tags that significantly increase the yields of target proteins in the periplasmic space are reviewed.

An ultra-dense library resource for rapid deconvolution of mutations that cause phenotypes in Escherichia coli

With the wide availability of whole-genome sequencing (WGS), genetic mapping has become the rate-limiting step, inhibiting unbiased forward genetics in even the most tractable model organisms. We introduce a rapid deconvolution resource and method for untagged causative mutations after mutagenesis, screens, and WGS in Escherichia coli. We created Deconvoluter—ordered libraries with selectable insertions every 50 kb in the E. coli genome. The Deconvoluter method uses these for replacement of untagged mutations in the genome using a phage-P1-based gene-replacement strategy. We validate the Deconvoluter resource by deconvolution of 17 of 17 phenotype-altering mutations from a screen of N-ethyl-N-nitrosourea-induced mutants. The Deconvoluter resource permits rapid unbiased screens and gene/function identification and will enable exploration of functions of essential genes and undiscovered genes/sites/alleles not represented in existing deletion collections. This resource for unbiased forward-genetic screens with mapping-by-sequencing (‘forward genomics’) demonstrates a strategy that could similarly enable rapid screens in many other microbes.

Cell factories for insulin production

The rapid increase in the number of diabetic patients globally and exploration of alternate insulin delivery methods such as inhalation or oral route that rely on higher doses, is bound to escalate the demand for recombinant insulin in near future. Current manufacturing technologies would be unable to meet the growing demand of affordable insulin due to limitation in production capacity and high production cost. Manufacturing of therapeutic recombinant proteins require an appropriate host organism with efficient machinery for posttranslational modifications and protein refolding. Recombinant human insulin has been produced predominantly using E. coli and Saccharomyces cerevisiae for therapeutic use in human. We would focus in this review, on various approaches that can be exploited to increase the production of a biologically active insulin and its analogues in E. coli and yeast. Transgenic plants are also very attractive expression system, which can be exploited to produce insulin in large quantities for therapeutic use in human. Plant-based expression system hold tremendous potential for high-capacity production of insulin in very cost-effective manner. Very high level of expression of biologically active proinsulin in seeds or leaves with long-term stability, offers a low-cost technology for both injectable as well as oral delivery of proinsulin.

Insulin related compounds and identification

Insulin-related compounds (IRCs), which originate during the expression and purification of human insulin using recombinant Escherichia coli, were purified and identified. We investigated the identity of IRCs and their origin. We also presented methods for inhibiting IRC formation. The strains used in this report were E. coli B5K and E. coli H27R. E. coli B5K had a 6-amino acid-fused peptide at the N-terminus of proinsulin, and E. coli H27R had a 28-amino acid-fused peptide at the N-terminus of proinsulin. We investigated the identity of IRCs and their origin by mainly using High Performance Liquid Chromatography (HPLC). The well-known IRCs, desamido human insulin and desthreonine human insulin, formed in both strains. In addition to these two IRCs, the B5K strain produced three different IRCs, Arg(A(0))-insulin (IRC 1), prepeptide-insulin (IRC 2), and Glu(A(22))-insulin (IRC 3). The amounts of IRC 1, IRC 2, IRC 3 were approximately 0.1-0.3% after final purification step. Among these IRCs, Arg(A(0))-insulin, prepeptide-insulin, and desthreonine insulin originated from incomplete enzyme reaction. Glu(A(22))-insulin was formed when we used a double stop codon during the expression of preproinsulin; that is, it was formed by the misreading of the first stop codon through the amber mutation. The major IRCs of the H27R strain were human insulin fragment (B1-B21) (IRC 4), and A9(Ser→Asn) amino acid single mutation human insulin (IRC 5), Arg(B(31))-insulin (IRC 6). Human insulin fragment (B1-B21) was formed by β-mercaptoethanol, which was added during refolding. It formed when the disulfide bonds between A-chain and B-chain of human insulin were cut by β-mercaptoethanol, followed by cleavage of the B-chain by trypsin and carboxypeptidase B. A9(Ser→Asn) amino acid single mutation human insulin originated from the mistranslation of A9 serine, such that asparagine was translated instead of serine. Arg(B(31))-insulin originated from incomplete enzyme reaction. The amount of IRC 4 was 10-15% after enzyme reaction. The amounts of IRC 5, IRC 6 were around 0.2% after final purification step. We present methods for inhibiting the formation of IRCs by controlling the amount of enzyme, controlling the rate of enzyme reaction, using a single stop codon, using hydrogen peroxide (H(2)O(2)) to inhibit β-mercaptoethanol, and modifying the A9 codon.

In vitro folding of methionine-arginine human lyspro-proinsulin S-sulfonate-disulfide formation pathways and factors controlling yield

We investigated the in vitro folding of an oxidized proinsulin (methionine-arginine human lyspro-proinsulin S-sulfonate), using cysteine as a reducing agent at 5°C and high pH (10.5-11). Folding intermediates were detected and characterized by means of matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS), reversed-phase chromatography (RPC), size-exclusion chromatography, and gel electrophoresis. The folding kinetics and yield depended on the protein and cysteine concentrations. RPC coupled with MALDI-MS analyses indicated a sequential formation of intermediates with one, two, and three disulfide bonds. The MALDI-MS analysis of Glu-C digested, purified intermediates indicated that an intra-A-chain disulfide bond formed first among A6, A7, and A11. Various non-native intra-A (A20 with A6, A7, or A11), intra-B (between B7 and B19), and inter-A-B disulfide bonds were observed in the intermediates with two disulfide bonds. The intermediates with three disulfide bonds had mainly the non-native intra-A and intra-B bonds. At a cysteine-to-proinsulin-SH ratio of 3.5, all intermediates with the non-native disulfide bonds were converted to properly folded proinsulin via disulfide bond reshuffling, which was the slowest step. Aggregation via the formation of intermolecular disulfide bonds of early intermediates was the major cause of yield loss. At a higher cysteine-to-proinsulin-SH ratio, some intermediates and folded MR-KPB-hPI were reduced to proteins with thiolate anions, which caused unfolding and even more yield loss than what resulted from aggregation of the early intermediates. Reducing protein concentration, while keeping an optimal cysteine-to-protein ratio, can improve folding yield significantly.

Increased expression, folding and enzyme reaction rate of recombinant human insulin by selecting appropriate leader peptide

Five new expression vectors for recombinant human insulin production (pPT-B5Kpi, pPT-T10Rpi, pPT-T13Rpi, pPT-H27Rpi, pPT-B5Rpi), which have different sizes and leader peptide structure, were constructed and compared based on their expression level, yields of S-sulfonated preproinsulin (SSPPI) and folded proinsulin and enzymatic conversion rate. The ranking of expression level of the five fused proinsulins was H27R≫T10R > B5K >T13R≈B5R. In particular, the expression level of H27R was more than double (60-70%) the level of the other fused proinsulins, and this high expression level led to large amounts of SSPPI, folded proinsulin and insulin. Changes to the leader peptide structure affected not only protein expression level, but also refolding yield because the leader peptide affects protein conformation and hydrophobicity. The refolding yield of H27R was 85% at 500L pilot scale. This high refolding yield was caused by the hydrophilic character of H27R. However, the β-mercaptoethanol concentration needed for refolding and the pH required to precipitate impurities after refolding had to be changed for high refolding yield. To avoid using CNBr, which is used to cleave fusion proteins, we used lysine and arginine linkers to connect the fusion protein and proinsulin. This fusion protein could be simultaneously cleaved by trypsin during enzymatic conversion to eliminate the C-peptide. The length and kind of leader peptide did not affect the enzyme reaction rate. Only the leader peptide linker connecting the B-chain influenced enzyme reaction rate. By testing several leader peptides, we constructed a new strain with 30% increased productivity based on expression level, refolding yield and enzyme reaction.

A review of advanced small-scale parallel bioreactor technology for accelerated process development: current state and future need

The pharmaceutical and biotech industries face continued pressure to reduce development costs and accelerate process development. This challenge occurs alongside the need for increased upstream experimentation to support quality by design initiatives and the pursuit of predictive models from systems biology. A small scale system enabling multiple reactions in parallel (n ≥ 20), with automated sampling and integrated to purification, would provide significant improvement (four to fivefold) to development timelines. State of the art attempts to pursue high throughput process development include shake flasks, microfluidic reactors, microtiter plates and small-scale stirred reactors. The limitations of these systems are compared to desired criteria to mimic large scale commercial processes. The comparison shows that significant technological improvement is still required to provide automated solutions that can speed upstream process development.

Model-based analysis and optimization of bioreactor for hematopoietic stem cell cultivation

One of the problems to be solved in attaining the full potentials of hematopoietic stem cell (HSC) applications is the limited availability of the cells. Growing HSCs in a bioreactor offers an alternative solution to this problem. Besides, it also offers the advantages of eliminating labour intensive process as well as the possible contamination involved in the periodic nutrient replenishments in the traditional T-flask stem cell cultivation. In spite of this, the optimization of HSC cultivation in a bioreactor has been barely explored. This manuscript discusses the development of a mathematical model to describe the dynamics in nutrient distribution and cell concentration of an ex vivo HSC cultivation in a microchannel perfusion bioreactor. The model was further used to optimize the cultivation by proposing three alternative feeding strategies in order to prevent the occurrence of nutrient limitation in the bioreactor. The evaluation of these strategies, the periodic step change increase in the inlet oxygen concentration, the periodic step change increase in the media inflow, and the feedback control of media inflow, shows that these strategies can successfully improve the cell yield of the bioreactor. In general, the developed model is useful for the design and optimization of bioreactor operation.

Application of simple fed-batch technique to high-level secretory production of insulin precursor using Pichia pastoris with subsequent purification and conversion to human insulin

Background

The prevalence of diabetes is predicted to rise significantly in the coming decades. A recent analysis projects that by the year 2030 there will be ~366 million diabetics around the world, leading to an increased demand for inexpensive insulin to make this life-saving drug also affordable for resource poor countries.

Results

A synthetic insulin precursor (IP)-encoding gene, codon-optimized for expression in P. pastoris, was cloned in frame with the Saccharomyces cerevisiae α-factor secretory signal and integrated into the genome of P. pastoris strain X-33. The strain was grown to high-cell density in a batch procedure using a defined medium with low salt and high glycerol concentrations. Following batch growth, production of IP was carried out at methanol concentrations of 2 g L^-1, which were kept constant throughout the remaining production phase. This robust feeding strategy led to the secretion of ~3 gram IP per liter of culture broth (corresponding to almost 4 gram IP per liter of cell-free culture supernatant). Using immobilized metal ion affinity chromatography (IMAC) as a novel approach for IP purification, 95% of the secreted product was recovered with a purity of 96% from the clarified culture supernatant. Finally, the purified IP was trypsin digested, transpeptidated, deprotected and further purified leading to ~1.5 g of 99% pure recombinant human insulin per liter of culture broth.

Conclusions

A simple two-phase cultivation process composed of a glycerol batch and a constant methanol fed-batch phase recently developed for the intracellular production of the Hepatitis B surface antigen was adapted to secretory IP production. Compared to the highest previously reported value, this approach resulted in an ~2 fold enhancement of IP production using Pichia based expression systems, thus significantly increasing the efficiency of insulin manufacture.

Synthesis of the human insulin gene: protein expression, scaling up and bioactivity

Optimized Synthetic human insulin gene was preferred to easy of cloning, plasmid stability, and protein expression away from the native sequence and its rare codons. Two steps to obtain the insulin, so we assembled the gene of 293 bp using a battery of overlapped synthetic oligos, then cloned into pET101directional TOPO expression vector downstream to the T7 promoter. The proinsulin products were produced as inclusion bodies in E. coli at a level of 10%. The batch cultivation of the strain yielded 6 g/L, while the high cell density of fed-batch cultivation yielded 46 g/L. The proinsulin purification yielded 110 mg/gram cell weight, and 1.3 mg/gram of a bioactive insulin. The native insulin was generated by enzymatic conversion of chemically processed proinsulin. The produced insulin was matched with that of a commercial aqueous version at a level of enzyme immunoassys, SDS-PAGE, RP-HPLC, and bioactivity. The present results showed that the produced insulin has a comparable biochemical and potency similar to that of commercial one.

Secretory expression of active clostripain in Escherichia coli

In this study, the clostripain gene was modified and its signal sequence was replaced with that of penicillin G acylase (PGA). The core clostripain protein fused to the PGA signal peptide was also prepared. With regard to the expression of the clostripain precursors, the majority of clostripain activity was observed in the culture media, thereby indicating that both the clostripain signal peptide and the PGA signal peptide were recognized in the E. coli secretion pathway, and the precursors successfully matured into the active form. Otherwise, the activity was rather low when the core protein was expressed, which indicates that the clostripain pro-peptide is important in the formation of the active enzyme in E. coli. Enzyme activity reached a value of 3200U/L in CGY media for high expression. The recombinant clostripain and porcine carboxypeptidase B were used in the conversion of a proinsulin fusion protein into insulin. The leader peptide (LP) and the proinsulin C-peptide appeared to have been removed simultaneously, and the final cleavage product evidenced an HPLC retention time identical to that of the insulin standard, thereby implying that the clostripain specifically cleaved the arginine residues in the LP and in the C-peptide. We have also demonstrated the possibility that the recombinant clostripain might prove useful in the production of insulin from the proinsulin fusion protein.

Methods for protecting silica sorbents used in high-performance liquid chromatography from strongly adsorbed impurities during purification of human recombinant insulin

One of the main stages of human recombinant insulin (HRI) production is the hormone purification by means of reversed phase high-performance liquid chromatography (RP HPLC). The optimization of this stage determines the increase of the total manufacturing yield. Therefore, the cost of the sorbent used in HPLC influences the cost of the manufacturing product, i.e. HRI substance. However, resolution between HRI and its admixtures decreases with time. The reason for this is the sorbent contamination with strongly adsorbed impurities (SAI) which are accumulated during elution. In the following research several methods for sorbent protection are studied. The opinion that SAI are mainly high-molecular weight compounds was examined using gel filtration. Different sorbent types were tested for the use in guard column. The results obtained were applied and improved at preparative level.

Development of a long-acting insulin analog using albumin fusion technology

The primary therapeutic goal for the treatment of diabetes is maintenance of a long-term, near-normoglycemic condition and prevention of the onset or progression of the complications associated with the disease. Although several analogs of human insulin have been developed, the currently prescribed long-acting insulin analogs do not provide a stable basal glycemia for more than a few hours. Here, we report the development of Albulin, a long-acting insulin analog obtained by direct gene fusion of a single-chain human insulin to human serum albumin. Albulin showed an elimination t(1/2) of approximately 7 h in normoglycemic mice. In vitro pharmacodynamic profiles for Albulin characterized by receptor binding, inhibition of gluconeogenesis, induction of glucose uptake, and global regulation of gene expression in relevant cell types showed that Albulin produced similar activity profiles compared with that of recombinant human insulin. A single Albulin administration in vivo normalized blood glucose level in diabetic mice in a relatively peakless and sustained (24-h) fashion. A further reduction in glucose levels was achieved by administering a recombinant human insulin a few hours after Albulin injection in mice, indicating the potential for Albulin therapy in combination with available fast-acting insulin derivatives. In summary, Albulin displays characteristics of a potent long-acting insulin analog that can be evaluated for use as a novel insulin therapy for patients with insulin-dependent diabetes.

Formation of disulfide bonds and homodimers of the major cat allergen Fel d 1 equivalent to the natural allergen by expression in Escherichia coli

Dander from the domestic cat (Felis domesticus) is one of the most common causes of IgE-mediated allergy. Attempts to produce tetrameric folded major allergen Fel d 1 by recombinant methods with structural features similar to the natural allergen have been only partially successful. In this study, a recombinant folded Fel d 1 with molecular and biological properties similar to the natural counterpart was produced. A synthetic gene coding for direct fusion of the Fel d 1 chain 2 N-terminally to chain 1 was constructed by overlapping oligonucleotides in PCR. Escherichia coli expression resulted in a non-covalently associated homodimer with an apparent molecular mass of 30 kDa defined by size exclusion chromatography. Furthermore, each 19,177-Da subunit displayed a disulfide pattern identical to that found in the natural Fel d 1, i.e. Cys3(1) Cys73(2), Cys44(1)-Cys48(2), Cys70(1)-Cys7(2), as determined by electrospray mass spectrometry after tryptic digestion. Circular dichroism analysis showed identical folds of natural and recombinant Fel d 1. Furthermore, recombinant Fel d l reacted specifically with serum IgE, inducing expression of CD203c on basophils and lymphoproliferative responses in cat-allergic patients. The results show that the overall fold and immunological properties of the recombinant Fel d 1 are very similar to those of natural Fel d 1. Moreover, the recombinant Fel d 1 construct provides a tool for defining the three-dimensional structure of Fel d 1 and represents a reagent for diagnosis and allergen-specific immunotherapy of cat allergy.

Strategies for the purification and on-column cleavage of glutathione-S-transferase fusion target proteins

In this report, we describe a flexible, efficient and rapid protein purification strategy for the isolation and cleavage of glutathione-S-transferase (GST) fusion proteins. The purification and on-column cleavage strategy was developed to work for the purification of difficult proteins and for target proteins where efficient fusion-tag cleavage is essential for downstream processes, such as structural and functional studies. To test and demonstrate the flexibility of this method, seven diverse unrelated target proteins were assayed. A purification technique is described that can be applied to a wide range of both soluble and membrane inserted recombinant target proteins of differing function, structure and chemical nature. This strategy is performed in a single chromatographic step applying an on-column cleavage method, yielding "native" proteins in the 200 microg to 40 mg/l scale of 95-98% purity.

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.

Recombinant human insulin. VIII. Isolation of fusion protein--S-sulfonate, biotechnological precursor of human insulin, from the biomass of transformed Escherichia coli cells

Various methods have been investigated for the isolation and purification of fusion proteins of precursors of human insulin in the form of S-sulfonates, from the biomass of transformed Escherichia coli cells. Fusion proteins were prepared with different sizes and structures of the leader peptide and the poly-His position (inserted for purification by metal chelate affinity chromatography). The fusion proteins contained an IgG-binding B domain of protein A from Staphylococcus aureus at the N-terminus and an Arg residue between the leader peptide of the molecule and the proinsulin sequence, for trypsin cleavage of the leader peptide. Six residues of Cys in proinsulin allow the chemical modification of the protein as a (Cys-S-SO(-)(3))(6) derivative (S-sulfonate), which increases its polyelectrolytic properties and improves the efficiency of its isolation. Various methods of oxidative sulfitolysis were compared with catalysis by sodium tetrathionate or cystine and Cu2+ or Ni2+ ions. An optimum scheme for the isolation and purification of S-sulfonated fusion proteins was developed by the combination of metal-chelating affinity and ion-exchange chromatography. Highly purified (95%) S-sulfonated fusion protein was recovered which was 85% of the fusion protein contained in the biomass of E. coli cells. Folding of fusion protein S-sulfonate occurred with high yield (up to 90-95%). We found that the fusion protein-S-sulfonate has proinsulin-like secondary structure. This structure causes highly efficient fusion protein folding.

Temperature-induced production of recombinant human insulin in high-cell density cultures of recombinant Escherichia coli

The construction of expression vectors encoding either the human insulin A- or B-chains fused to a synthetic peptide and the temperature-induced expression of the recombinant genes in Escherichia coli are reported. Using this two-chain approach we also describe the separate isolation of the insulin A- and B-chains from inclusion bodies and their subsequent assembly into native human insulin. The production of the insulin fusion proteins were carried out in high-cell density fed-batch cultures using a synthetic medium with glucose as sole carbon and energy source. The expression of the recombinant genes by temperature-shift in high-cell density cultures of recombinant E. coli resulted in product yields of grams per litre of culture broth, e.g. 4.5 g of insulin B-chain fusion protein per litre of culture broth. This translates into an expression yield of about 800 mg of the insulin B-chain per litre of culture. Under similar cultivation conditions the expression yield of the insulin A-chain corresponds to approximately 600 mg per litre of culture. The metabolic burden imposed on the recombinant cells during temperature-induced production of insulin fusion proteins in high-cell density cultures is reflected in an increased respiratory activity and a reduction of the biomass yield coefficient with respect to glucose.

Gene fragment polymerization gives increased yields of recombinant human proinsulin C-peptide

A multimerization strategy to improve yields upon recombinant production of the 31-aa human proinsulin C-peptide is presented. Gene fragments encoding the C-peptide were assembled using specific head-to-tail multimerization. DNA constructs encoding one, three or seven copies of the C-peptide gene, fused to a serum albumin binding affinity tag, were expressed intracellularly in Escherichia coli. The three fusion proteins were produced at similar levels (approximately 50 mg/l) and were proteolytically stable during production. Enzymatic digestion by trypsin-carboxypeptidase B treatment of the fusion proteins was shown to efficiently release native C-peptide, as determined by mass spectrometry, reverse-phase chromatography and a radioimmunoassay. The quantitative yields of C-peptide obtained from the three different fusion proteins suggest that this multimerization strategy could provide a cost-efficient production scheme for the C-peptide, and that this strategy could be useful also for production of other recombinant peptides.