Affinity-assisted in vivo folding of a secreted human peptide hormone in Escherichia coli

Using folding promoting agents in recombinant protein production: a review

Recombinant production has become an invaluable tool for supplying research and therapy with proteins of interest. The target proteins are not in every case soluble and/or correctly folded. That is why different production parameters such as host, cultivation conditions and co-expression of chaperones and foldases are applied in order to yield functional recombinant protein. There has been a constant increase and success in the use of folding promoting agents in recombinant protein production. Recent cases are reviewed and discussed in this chapter. Any impact of such strategies cannot be predicted and has to be analyzed and optimized for the corresponding target protein. The in vivo effects of the agents are at least partially comparable to their in vitro mode of action and have been studied by means of modern systems approaches and even in combination with folding/activity screening assays. Resulting data can be used directly for experimental planning or can be fed into knowledge-based modelling. An overview of such technologies is included in the chapter in order to facilitate a decision about the potential in vivo use of folding promoting agents.

Recombinant protein secretion in Escherichia coli

The secretory production of recombinant proteins by the Gram-negative bacterium Escherichia coli has several advantages over intracellular production as inclusion bodies. In most cases, targeting protein to the periplasmic space or to the culture medium facilitates downstream processing, folding, and in vivo stability, enabling the production of soluble and biologically active proteins at a reduced process cost. This review presents several strategies that can be used for recombinant protein secretion in E. coli and discusses their advantages and limitations depending on the characteristics of the target protein to be produced.

Evaluation of bottlenecks in proinsulin secretion by Escherichia coli

This work evaluates three potential bottlenecks in recombinant human proinsulin secretion by Escherichia coli: protein stability, secretion capacity and the effect of molecular size on secretion efficiency. A maximum secretion level of 7.2 mg g(-1) dry cell weight was obtained in the periplasm of E. coli JM109(DE3) host cells. This value probably represents an upper limit in the transport capacity of E. coli cells secreting ZZ-proinsulin and similar proteins with the protein A signal peptide. A selective deletion study was performed in the fusion partner and no effect of the molecular size (17-24 kDa) was detected on secretion efficiency. The protective effect against proteolysis provided by the ZZ domain was thoroughly demonstrated in the periplasm of E. coli and it was also shown that a single Z domain is able to provide the same protection level without compromising the downstream processing. The use of this shorter fusion partner enables a 1.6-fold increase in the recovery of the target protein after cleavage of the affinity handle.

Recombinant expression and in vitro folding of proinsulin are stimulated by the synthetic dithiol Vectrase-P

Recombinant production of native proinsulin in the periplasm of Escherichia coli is limited by formation of the correct disulfide bonds and inclusion body formation. These limitations can be overcome during in vitro folding of proinsulin by using a redox system and also protein disulfide isomerase. Here, we added a redox active substance, Vectrase-P, to the cultivation medium of E. coli cells producing proinsulin. We show that this synthetic dithiol partially mimicking the redox activity of protein disulfide isomerase provides an improved redox situation in the periplasm and, therefore, provides optimum conditions for folding of proinsulin in that cell compartment resulting in an increase in yield of 60%. The in vivo results were confirmed by analyzing in vitro folding of proinsulin in the presence of the dithiol Vectrase-P.

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.

Expression of the second epidermal growth factor-like domain of human factor VII in Escherichia coli

The second epidermal growth factor (EGF)-like domain of human coagulation factor VII is a potent inhibitor of the FVIIa/tissue factor complex, the predominant initiator of coagulation in vivo. This domain has now for the first time been cloned and expressed in Escherichia coli as an affinity fusion protein. The fusion protein was secreted into the periplasm of E. coli and purified by affinity chromatography. The purified protein consisted of a fusion protein with the expected molecular weight, and in addition, a significant fraction of oligomers cross-linked by intermolecular disulfide bonds. Despite the presence of oligomers, the purified protein was a potent inhibitor of the extrinsic blood coagulation pathway with an IC50 value of about 20 microM. The biological activity was retained after liberation of the EGF domain by proteolytic cleavage.

Binding proteins selected from combinatorial libraries of an alpha-helical bacterial receptor domain

Small protein domains, capable of specific binding to different target proteins have been selected using combinatorial approaches. These binding proteins, called affibodies, were designed by randomization of 13 solvent-accessible surface residues of a stable alpha-helical bacterial receptor domain Z, derived from staphylococcal protein A. Repertoires of mutant Z domain genes were assembled and inserted into a phagemid vector adapted for monovalent phage display. Two libraries, each comprising approximately 4 x 10(7) transformants, were constructed using either an NN(G/T) or an alternative (C/A/G)NN degeneracy. Biopanning against the target proteins Taq DNA polymerase, human insulin, and a human apolipoprotein A-1 variant, showed that in all cases significant enrichments were obtained by the selection procedures. Selected clones were subsequently expressed in Escherichia coli and analyzed by SDS-PAGE, circular dichroism spectroscopy, and binding studies to their respective targets by biospecific interaction analysis. The affibodies have a secondary structure similar to the native Z domain and have micromolar dissociation constants (KD) for their respective targets.