Cloning, expression, and characterization of diuretic hormone Manduca diuresin from Manduca sexta in Escherichia coli

Functional small peptides for enhanced protein delivery, solubility, and secretion in microbial biotechnology

In microbial biotechnology, there is a constant demand for functional peptides to give new functionality to engineered proteins to address problems such as direct delivery of functional proteins into bacterial cells, enhanced protein solubility during the expression of recombinant proteins, and efficient protein secretion from bacteria. To tackle these critical issues, we selected three types of functional small peptides: cell-penetrating peptides (CPPs) enable the delivery of diverse cargoes into bacterial cytoplasm for a variety of purposes, protein-solubilizing peptide tags demonstrate remarkable efficiency in solubilizing recombinant proteins without folding interference, and signal peptides play a key role in enabling the secretion of recombinant proteins from bacterial cells. In this review, we introduced these three functional small peptides that offer effective solutions to address emerging problems in microbial biotechnology. Additionally, we summarized various engineering efforts aimed at enhancing the activity and performance of these peptides, thereby providing valuable insights into their potential for further applications.

Efficient extracellular production of recombinant proteins in E. coli via enhancing expression of dacA on the genome

D, D-carboxypeptidase DacA plays an important role in the synthesis and stabilization of Escherichia coli cell wall peptidoglycan. The production level of extracellular recombinant proteins in E. coli can be enhanced by high D, D-carboxypeptidase activity. Construction of expression systems under optimal promoters is one of the main strategies to realize high protein production in E. coli. In this study, the promoter PdacA-3 from DacA on the genome of E. coli BL21 (DE3) was verified to be efficient for recombinant green fluorescent protein using the plasmid mutant pET28a-PdacA with PdacA-3. Meanwhile, the promoter PdacA-3 was engineered to increase the production level of proteins via inserting one or two Shine-Dalgarno (SD) sequences between the promoter PdacA-3 and the target genes. The expression level of dacA on the genome was increased by the improved transcription of the engineered promoters (especially after inserting one additional SD sequence). The engineered promoters increased cell membrane permeabilities to significantly enhance the secretion production of extracellular recombinant proteins in E. coli. Among them, the extracellular recombinant amylase activities in E. coli BL21::1SD-pET28a-amyK and E. coli BL21::2SD-pET28a-amyK were increased by 2.0- and 1.6-fold that of the control (E. coli BL21-pET28a-amyK), respectively. Promoter engineering also affected the morphology and growth of the E. coli mutants. It was indicated that the engineered promoters enhanced the expression of dacA on the genome to disturb the synthesis and structural stability of cell wall peptidoglycans.

High yield production of the latex clearing protein from Gordonia polyisoprenivorans VH2 in fed batch fermentations using a recombinant strain of Escherichia coli

The enzymatic degradation of rubber with the latex clearing protein (Lcp1_VH2) from Gordonia polyisoprenivorans VH2, is a promising option as an environmentally friendly and economical solution to treat the enormous amount of rubber waste. Here we present a fed batch fermentation process on a 10 L scale, using E.coli C41 pET23a(+)::Hislcp1_VH2 and a modified defined mineral salt medium, designed for high cell densities, for a proper synthesis of Lcp1_VH2. Particularly, providing complex media components, as well as hemin, as precursor of the essential heme b cofactor, resulted in a 2.9-fold higher yield of active Lcp1_VH2 with increased specific activity, due to a better occupancy of the enzyme with the cofactor. Based on this optimization, the fed batch fermentation with an initial glucose feed, followed by a lactose-glycerol feed, finally gained a cell dry weight of 60 g L^-1 and a yield of 223 mg L^-1 of soluble, active Lcp1_VH2. Compared to a recently published fermentation process, which used a complex auto-induction medium, we significantly increased the biomass up to nearly 10-fold and the total Lcp1_VH2 yield up to 3.7-fold. Thereby we reduced the costs for the medium by 75 %, taking the next step towards industrial production of rubber degrading enzymes.

A revolutionary approach facilitating co-expression of authentic human epidermal growth factor and basic fibroblast growth factor in both cytoplasm and culture medium of Escherichia coli

During secretory or excretory production of heterologous proteins in Escherichia coli, peptidase processing cleaves the signal peptide off from a premature protein, which is then secreted as a mature product. Many proteins have been successfully expressed as secreted/excreted products in E. coli. However, basic fibroblast growth factor (bFGF), despite its suitability for secretory/excretory production in E. coli, has never been successfully expressed using such an approach. In this communication, we report the application of a revolutionary E. coli system to the efficient expression of not only bFGF, but also human epidermal growth factor (EGF) concurrently, as authentic products in the culture supernatant (SN). More interestingly, both polypeptides were also shown to be present at high levels as authentic products in the cell lysate (CL). The manifestation of this unusual phenomenon required a collaborative action between construct pWKW2, an efficient excretion vector engineered by our group to facilitate extracellular production of EGF, and the Sce VMA intein, which enables self-cleavage of protein sequences fused to it. Both bFGF and EGF derived from SN and CL were characterized to be bioactive. Moreover, despite employing only shake-flask cultivation, the total yields of bFGF and EGF recovered from both SN and CL were impressive, amounting to 103 and 74 mg l(-1) of culture, respectively. The novel expression approach introduced herein may prove to be practically useful for the production of a wide range of proteins in the future.

Design of a Peptibody Consisting of the Antimicrobial Peptide dhvar5 and a llama Variable Heavy-chain Antibody Fragment

Immunoconjugates have been widely studied as potential therapeutics for infectious diseases to direct unspecific antimicrobials to pathogens. In this study, the recombinant approach was used for expression of the immunoconjugate composed of the variable domain of a llama heavy-chain antibody (VHH) against Streptococcus mutans and dhvar5, a synthetic antimicrobial peptide. Before cloning, the impact of the elongation of the peptide termini on its biological activity was evaluated by chemical synthesis of the N- or C-termini extended dhvar5 peptides. As the elongation of the C-terminus had a greater influence on decline of the antimicrobial activity, the N-terminal fusion was designed. To promote in vivo release of the active peptide, a factor Xa cleavage site was inserted between VHH and dhvar5. Propagation of transformed Escherichia coli with the constructed plasmid was only possible in the absence of isopropyl beta-D-thiogalactoside (IPTG). Although these data demonstrate that the diminished antimicrobial activity of dhvar5 by the N-terminal fusion to VHH was not sufficient for the protection of the bacterial host cells against the peptide lethal effect, an insight into propeptides biological activities may be beneficial not only for new and more successful rearrangement of the VHH-dhvar5 immunoconjugate construct, but also design of the other recombinant molecules composed of peptides toxic to host cells.