Connection between gene dosage and protein stability revealed by a high-yield production of recombinant proteins in an E. coli LexA1(Ind-) background

Sense and nonsense from a systems biology approach to microbial recombinant protein production

The 'Holy Grail' of recombinant protein production remains the availability of generic protocols and hosts for the production of even the most difficult target products. The present review provides first an explanation why the shock imposed on bacteria using a standard induction protocol not only arrests growth, but also decreases the number of colony-forming units by several orders of magnitude. Particular emphasis is placed on findings of numerous genome-wide transcriptomic studies that highlight cellular stress, in which the general stress, heat-shock and stringent responses are the underlying basis for the manifestation of the deterioration of cell physiology. We then review common approaches used to solve bottlenecks in protein folding and post-translational modification that result in recombinant protein deposition in cytoplasmic inclusion bodies. Finally, we suggest a generic approach to process design that minimizes stress on the production host and a strategy for isolating improved hosts.

Lon and ClpP proteases participate in the physiological disintegration of bacterial inclusion bodies

Aggregated protein is solubilized by the combined activity of chaperones ClpB, DnaK and small heat-shock proteins, and this could account, at least partially, for the physiological disintegration of bacterial inclusion bodies. In vivo, the involvement of proteases in this process had been suspected but not investigated. By using an aggregation prone beta-galactosidase fusion protein produced in Escherichia coli, we show in this study that the main ATP-dependent proteases Lon and ClpP participate in the physiological disintegration of cytoplasmic inclusion bodies, their absence minimizing the protein removal up to 40%. However, the role of these proteases is clearly distinguishable especially regarding the fate of solubilized protein. While Lon appears as a minor contributor in the disintegration process, ClpP directs an important attack on the released or releasable protein even not being irreversibly misfolded. ClpP is then observed as a wide-spectrum, main processor of aggregation-prone proteins and also of polypeptides physiologically released from inclusion bodies, even when occurring as soluble versions with a conformation compatible with their enzymatic activity.

Enhanced expression of a recombinant malaria candidate vaccine in Escherichia coli by codon optimization

This study was conducted to compare the expression of three constructs of a multistage candidate vaccine (FALVAC-1) against Plasmodium falciparum in an Escherichia coli system: a synthetic gene with P. falciparum codons, a synthetic gene with optimized E. coli codons, and a synthetic gene with P. falciparum codons co-transformed with a RIG plasmid, which encodes three tRNAs (AG(A/G), ATA, GGA) that recognize rare E. coli codons. The expression of the protein increased at least threefold with codon optimization. The presence of the RIG plasmid in the co-transforming cells did not significantly increase the expression level of the gene with P. falciparum codons. The growth of cells transformed by the construct with P. falciparum codons was significantly slower than that of cells transformed by the construct with optimized E. coli codons after induction of protein expression with IPTG. The cells containing the non-codon optimized gene co-expressed with RIG plasmid had the slowest growth at all time points in culture. Thus, codon optimization significantly increases the yield of P. falciparum candidate vaccines in the E. coli expression system.