Expression and characterization of a housefly cecropin gene in the methylotrophic yeast, Pichia pastoris

The dual interaction of antimicrobial peptides on bacteria and cancer cells; mechanism of action and therapeutic strategies of nanostructures

Microbial infection and cancer are two leading causes of global mortality. Discovering and developing new therapeutics with better specificity having minimal side-effects and no drug resistance are of an immense need. In this regard, cationic antimicrobial peptides (AMP) with dual antimicrobial and anticancer activities are the ultimate choice. For better efficacy and improved stability, the AMPs available for treatment still required to be modified. There are several strategies in which AMPs can be enhanced through, for instance, nano-carrier application with high selectivity and specificity enables researchers to estimate the rate of drug delivery to a particular tissue. In this review we present the biology and modes of action of AMPs for both anticancer and antimicrobial activities as well as some modification strategies to improve the efficacy and selectivity of these AMPs.

In vitro Impact of Yeast Expressed Hybrid Peptide CATH-2TP5 as a Prophylactic Measure Toward Sepsis and Inflammation

CATH-2TP5 is a linear cationic hybrid peptide, consequent from naturally occurring antimicrobial peptide (AMPs) Cathelicidin-2 (CATH-2) and Immunomodulatory peptide Thymopentin (TP5) having dynamic and potent anti-inflammatory activities without hemolytic effect. The biocompatible mechanism of CATH-2TP5 is favored to explore new methodologies in the direction of biomedical applications. In this retrospectively study, an antiendotoxin and anti-inflammatory hybrid peptide CATH-2TP5 was emulated into pPICZα-A and successfully expressed in Pichia pastoris (P. pastoris). The recombinant CATH-2TP5 was purified through the Ni-affinity column and reversed-phase HPLC. The purified CATH-2TP5 peptide exhibited robust anti-endotoxin activity and significantly (p < 0.05) neutralized the effect of lipopolysaccharide (LPS). Furthermore, the down-regulated effect of CATH-2TP was more pronounced (p < 0.05) on LPS-induced cytotoxic effects, nitric oxide secretion and pro-inflammatory cytokines (TNF-α, IL-6, and IL-1β) in murine RAW264.7 macrophages. As associated to control and parental peptide the number of apoptotic cells was also contracted with the treatment of CATH-2TP5. Thus, we concluded that CATH-2TP5 peptide may be used in various biomedical applications as a therapeutic drug.

Antimicrobial functional divergence of the cecropin antibacterial peptide gene family in Musca domestica

BACKGROUND

It has been reported that there are more than ten antimicrobial peptides (AMPs) belonging to the cecropin family in Musca domestica; however, few of them have been identified, and the functions of the other molecules are poorly understood.

METHODS

Sequences of the M. domestica cecropin family of genes were cloned from cDNA template, which was reverse-transcribed from total mRNA isolated from third-instar larvae of M. domestica that were challenged with pathogens. Sequence analysis was performed using DNAMAN comprehensive analysis software, and a molecular phylogenetic tree of the cecropin family was constructed using the Neighbour-Joining method in MEGA v.5.0 according to the mature peptide sequences. Antibacterial activity of the synthetic M. domestica cecropin protein was detected and the minimum inhibitory concentration (MIC) values were determined using broth microdilution techniques. Time-killing assays were performed on the Gram-negative bacteria, Acinetobacter baumannii, at the logarithmic or stabilizing stages of growth, and its morphological changes when treated with Cec4 were assessed by scanning electron microscopy (SEM) and detection of leakage of 260 nm absorbing material.

RESULTS

Eleven cecropin family genes, namely Cec01, Cec02 and Cec1-9, show homology to the Cec form in a multigene family on the Scaffold18749 of M. domestica. In comparing the encoded cecropin protein sequences, most of them have the basic characteristics of the cecropin family, containing 19 conservative amino acid residues. To our knowledge, this is the first experimental demonstration that most genes in the Cec family are functional. Cec02, Cec1, Cec2, Cec5 and Cec7 have similar antibacterial spectra and antibacterial effects against Gram-negative bacteria, while Cec4 displays a more broad-spectrum of antimicrobial activity and has a very strong effect on A. baumannii. Cec4 eliminated A. baumannii in a rapid and concentration-dependent manner, with antibacterial effects within 24 h at 1× MIC and 2× MIC. Furthermore, SEM analysis and the leakage of 260 nm absorbing material detection indicated that Cec4 sterilized the bacteria through the disruption of cell membrane integrity.

CONCLUSIONS

Although there are more than ten cecropin genes related to M. domestica, some of them have no preferred antibacterial activity other than Cec4 against A. baumannii.

Molecular Identification of a Moricin Family Antimicrobial Peptide (Px-Mor) From Plutella xylostella With Activities Against the Opportunistic Human Pathogen Aureobasidium pullulans

Antimicrobial peptides (AMPs) represent the largest group of endogenous compounds and serves as a novel alternative to traditional antibiotics for the treatment of pathogenic microorganisms. Moricin is an important α-helical AMP plays a crucial role in insect humoral defense reactions. The present study was designed to identify and characterize novel AMP moricin (Px-Mor) from diamondback moth (Plutella xylostella) and tested its activity against bacterial and fungal infection including the opportunistic human pathogen Aureobasidium pullulans. Molecular cloning of Px-Mor using rapid amplification of cDNA ends revealed a 482 bp full length cDNA with 198 bp coding region. The deduced protein sequence contained 65 amino acids, and the mature peptides contained 42 amino acid residues with a molecular mass of 4.393 kDa. Expression analysis revealed that Px-Mor was expressed throughout the life cycle of P. xylostella with the highest level detectable in the fourth instar and prepupa stage. Tissue specific distribution showed that Px-Mor was highly expressed in fat body and hemocyte. In vitro, antimicrobial assays indicated that Px-Mor exhibited a broad antimicrobial spectrum against Gram positive bacteria (GPB), Gram negative bacteria (GNB) and fungi. Moreover, scanning electron microscopy and transmission electron microscopy (TEM) revealed that Px-Mor can cause obvious morphological alterations in A. pullulans, which demonstrated its powerful effect on the mycelia growth inhibition. Taken together, these results indicate that Px-Mor plays an important role in the immune responses of P. xylostella and can be further exploited as an antimicrobial agent against various diseases including for the treatment of A. pullulans infection.

Biotechnological Production of the Cell Penetrating Antifungal PAF102 Peptide in Pichia pastoris

Antimicrobial peptides (AMPs) have potent and durable antimicrobial activity to a wide range of fungi and bacteria. The growing problem of drug-resistant pathogenic microorganisms, together with the lack of new effective compounds, has stimulated interest in developing AMPs as anti-infective molecules. PAF102 is an AMP that was rationally designed for improved antifungal properties. This cell penetrating peptide has potent and specific activity against major fungal pathogens. Cecropin A is a natural AMP with strong and fast lytic activity against bacterial and fungal pathogens, including multidrug resistant pathogens. Both peptides, PAF102 and Cecropin A, are alternative antibiotic compounds. However, their exploitation requires fast, cost-efficient production systems. Here, we developed an innovative system to produce AMPs in Pichia pastoris using the oleosin fusion technology. Oleosins are plant-specific proteins with a structural role in lipid droplet formation and stabilization, which are used as carriers for recombinant proteins to lipid droplets in plant-based production systems. This study reports the efficient production of PAF102 in P. pastoris when fused to the rice plant Oleosin 18, whereas no accumulation of Cecropin A was detected. The Ole18-PAF102 fusion protein targets the lipid droplets of the heterologous system where it accumulates to high levels. Interestingly, the production of this fusion protein induces the formation of lipid droplets in yeast cells, which can be additionally enhanced by the coexpression of a diacylglycerol transferase gene that allows a three-fold increase in the production of the fusion protein. Using this high producer strain, PAF102 reaches commercially relevant yields of up to 180 mg/l of yeast culture. Moreover, the accumulation of PAF102 in the yeast lipid droplets facilitates its downstream extraction and recovery by flotation on density gradients, with the recovered PAF102 being biologically active against pathogenic fungi. Our results demonstrate that plant oleosin fusion technology can be transferred to the well-established P. pastoris cell factory to produce the PAF102 antifungal peptide, and potentially other AMPs, for multiple applications in crop protection, food preservation and animal and human therapies.

Screening, Expression, Purification and Functional Characterization of Novel Antimicrobial Peptide Genes from Hermetia illucens (L.)

Antimicrobial peptides from a wide spectrum of insects possess potent microbicidal properties against microbial-related diseases. In this study, seven new gene fragments of three types of antimicrobial peptides were obtained from Hermetia illucens (L), and were named cecropinZ1, sarcotoxin1, sarcotoxin (2a), sarcotoxin (2b), sarcotoxin3, stomoxynZH1, and stomoxynZH1(a). Among these genes, a 189-basepair gene (stomoxynZH1) was cloned into the pET32a expression vector and expressed in the Escherichia coli as a fusion protein with thioredoxin. Results show that Trx-stomoxynZH1 exhibits diverse inhibitory activity on various pathogens, including Gram-positive bacterium Staphylococcus aureus, Gram-negative bacterium Escherichia coli, fungus Rhizoctonia solani Khün (rice)-10, and fungus Sclerotinia sclerotiorum (Lib.) de Bary-14. The minimum inhibitory concentration of Trx-stomoxynZH1 is higher against Gram-positive bacteria than against Gram-negative bacteria but similar between the fungal strains. These results indicate that H. illucens (L.) could provide a rich source for the discovery of novel antimicrobial peptides. Importantly, stomoxynZH1 displays a potential benefit in controlling antibiotic-resistant pathogens.

Recombinant expression and biological characterization of the antimicrobial peptide fowlicidin-2 in Pichia pastoris

Fowlicidins are a group of cathelicidin antimicrobial peptides that were initially identified in chickens. Fowlicidin-2, which is composed of 31 amino acids, is widely expressed in the majority of tissues in chickens and has an important role in innate immunity. In the present study, a recombinant expression system for fowlicidin-2 was successfully constructed using Pichia pastoris X-33 and the expression vector pPICZα-A. Under the optimized fermentation conditions, 85.6 mg fowlicidin-2 with >95% purity was obtained from 1 liter culture medium following purification by ion exchange chromatography and reversed phase high performance liquid chromatography. The recombinant fowlicidin-2 exhibited broad spectrum antimicrobial activity and had a minimum inhibitory concentration ranging from 1 to 4 µM. Furthermore, recombinant fowlicidin-2 exhibited hemolytic activity, promoting 50% human erythrocyte hemolysis in the concentration range of 128-256 µM, and anticancer activity, resulting in the death of 50% of A375 human malignant melanoma cells in the concentration range of 2-4 µM. The results of the present study suggest that recombinant fowlicidin-2 may be a promising candidate for therapeutic applications.

Expression and purification of FGF21 in Pichia pastoris and its effect on fibroblast-cell migration

Fibroblast growth factor (FGF)21 functions in the maintenance of glucose homeostasis and exerts protective effects on the liver, heat and kidneys. However, the roles of FGF21 in other tissue types are yet to be fully elucidated. The present study detected elevated expression levels of FGF21 in skin tissue. Furthermore, it was revealed that FGF21 expression in the skin was induced upon wounding. In addition, β‑klotho expression was detected in the skin tissue. To examine the role of FGF21 in the wound healing process, recombinant human (h)FGF21 was expressed in a the yeast strain Pichia (P.) pastoris, a well‑known system for recombinant protein production. Based on the sequence of hFGF21 and the optimal codon of P. pastoris, codon‑optimized FGF21 open reading frame sequences were obtained using seven pairs of 55‑59‑nt primers with seven rounds of PCR. The recombinant FGF21 was purified and its function was examined in human fibroblast cells using a wound healing cell migration assay. Treatment with FGF21 promoted cell migration, which is an important step in wound healing. Furthermore, FGF21 treatment enhanced the activity of c‑Jun N‑terminal kinase, a key regulator in fibroblast‑cell migration. In conclusion, FGF21 is induced after wounding and FGF21 expressed and purified from yeast markedly accelerates wound healing. The present study was the first to elucidate the function of FGF21 in skin tissues and provided a theoretical basis for the use of FGF21 in the treatment of skin wounds.

Cecropins from Plutella xylostella and Their Interaction with Metarhizium anisopliae

Cecropins are the most potent induced peptides to resist invading microorganisms. In the present study, two full length cDNA encoding cecropin2 (Px-cec2) and cecropin3 (Px-cec3) were obtained from P. xylostella by integrated analysis of genome and transcriptome data. qRT-PCR analysis revealed the high levels of transcripts of Px-cecs (Px-cec1, Px-cec2 and Px-cec3) in epidermis, fat body and hemocytes after 24, 30 and 36 h induction of Metarhizium anisopliae, respectively. Silencing of Spätzle and Dorsal separately caused the low expression of cecropins in the fat body, epidermis and hemocytes, and made the P.xylostella larvae more susceptible to M. anisopliae. Antimicrobial assays demonstrated that the purified recombinant cecropins, i.e., Px-cec1, Px-cec2 and Px-cec3, exerted a broad spectrum of antimicrobial activity against fungi, as well as Gram-positive and Gram-negative bacteria. Especially, Px-cecs showed higher activity against M. anisopliae than another selected fungi isolates. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed that cecropins exerted the vital morphological alterations to the spores of M. anisopliae. Based on our results, cecropins played an imperative role in resisting infection of M. anisopliae, which will provide the foundation of biological control of insect pests by using cecorpins as a target in the future.

Characterization of bioactive recombinant antimicrobial peptide parasin I fused with human lysozyme expressed in the yeast Pichia pastoris system

Parasin I (PI) is a 19 amino acid peptide with potent antimicrobial activities against a broad spectrum of microorganisms and is a good candidate for development as a novel antimicrobial agent. The objective of this study was to express and characterize a codon optimized parasin I peptide fused with human lysozyme (hLY). A 513 bp cDNA fragment encoding the mature hLY protein and parasin I peptide was designed and synthesized according to the codon bias of Pichia pastoris. A 4×Gly flexible amino acid linker with an enterokinase cleavage (DDDDK) was designed to link the PI to the C-terminal of hLY. The codon optimized recombinant hLY-PI was cloned into the pPICZαA vector and expressed in P. pastoris. The over-expressed extracellular rehLY-PI was purified using Ni sepharose affinity column and exhibited a molecular mass of approximately 18 kDa. After digested with enterokinase the rehLY-PI protein release its corresponding rehLY and rePI, with molecular mass of 16 kDa and 2 kDa, respectively, on Tricine-SDS-PAGE. The released rehLY exhibited similar lytical activity against Micrococcus lysodeikticus to its commercial hLY. The digested rehLY-PI product exhibited antimicrobial activities against Bacillus subtilis, Staphylococcus aureus and Escherichia coli, and synergism has been found between the released rePI and rehLY. In conclusion, we successfully optimized a rehLY-PI fusion protein encoding gene and over-expressed the rehLY-PI in P. pastoris. The recombination protein digested with enterokinase released functional hLY and antimicrobial parasin I, which demonstrates a potential for future use as an animal feed additive to partly replace antibiotic.

Expression of porcine protegrin-1 in Pichia pastoris and its anticancer activity in vitro

Protegrin-1 (PG-1), a β-hairpin antimicrobial peptide (AMP), is amongst the shortest AMPs in sequence length while remaining active against a variety of microorganisms. The aim of this study was produce recombinant PG-1 and investigate its anticancer activity. A DNA sequence encoding the mature PG-1, fused with a 6His-tag, was cloned into the pPICZα-A vector and transformed into Pichia pastoris. Expression was induced following culture for ~96 h with 1% methanol at 28°C, and ~15.6 mg PG-1 was expressed in 100 ml culture medium. Following purification using a Ni-chelating Sepharose column, ~20 mg pure active PG-1 was obtained from 500 ml culture broth supernatant. The expressed PG-1/6His exhibited strong dose- and time-dependent anticancer activity against HepG2 cells in vitro.

Protein expression in Pichia pastoris: recent achievements and perspectives for heterologous protein production

Pichia pastoris is an established protein expression host mainly applied for the production of biopharmaceuticals and industrial enzymes. This methylotrophic yeast is a distinguished production system for its growth to very high cell densities, for the available strong and tightly regulated promoters, and for the options to produce gram amounts of recombinant protein per litre of culture both intracellularly and in secretory fashion. However, not every protein of interest is produced in or secreted by P. pastoris to such high titres. Frequently, protein yields are clearly lower, particularly if complex proteins are expressed that are hetero-oligomers, membrane-attached or prone to proteolytic degradation. The last few years have been particularly fruitful because of numerous activities in improving the expression of such complex proteins with a focus on either protein engineering or on engineering the protein expression host P. pastoris. This review refers to established tools in protein expression in P. pastoris and highlights novel developments in the areas of expression vector design, host strain engineering and screening for high-level expression strains. Breakthroughs in membrane protein expression are discussed alongside numerous commercial applications of P. pastoris derived proteins.

Current scenario of peptide-based drugs: the key roles of cationic antitumor and antiviral peptides

Cationic antimicrobial peptides (AMPs) and host defense peptides (HDPs) show vast potential as peptide-based drugs. Great effort has been made in order to exploit their mechanisms of action, aiming to identify their targets as well as to enhance their activity and bioavailability. In this review, we will focus on both naturally occurring and designed antiviral and antitumor cationic peptides, including those here called promiscuous, in which multiple targets are associated with a single peptide structure. Emphasis will be given to their biochemical features, selectivity against extra targets, and molecular mechanisms. Peptides which possess antitumor activity against different cancer cell lines will be discussed, as well as peptides which inhibit virus replication, focusing on their applications for human health, animal health and agriculture, and their potential as new therapeutic drugs. Moreover, the current scenario for production and the use of nanotechnology as delivery tool for both classes of cationic peptides, as well as the perspectives on improving them is considered.

Expression, purification and characterization of cecropin antibacterial peptide from Bombyx mori in Saccharomyces cerevisiae

CecropinXJ is a cationic antimicrobial peptide originally isolated from the larvae of Bombyx mori. In this study, an antibacterial peptide gene of cecropinXJ was cloned into the pYES2/CT/α Factor expression vector and expressed in the Saccharomyces cerevisiae INVSc1 strain. Following an induction of recombinant protein expression in yeast for 120 h, the maximum amount of total secreted protein was 1.437 g/L. The percentage of recombinant cecropinXJ was estimated to be 79.45% of the total protein. After purification with Ni-NTA agarose column, recombinant cecropinXJ was noted to exert strong antimicrobial activities against a broad-spectrum of microorganisms, including Gram-negative and Gram-positive bacteria. Its minimal inhibitory concentration (MIC) against Escherichia coli ATCC25922 was 0.81 μM. In addition, transmission electron microscopy (TEM) analysis indicated that the surfaces of the treated pathogens underwent obvious morphological changes compared with the untreated controls, suggesting that this antimicrobial peptide exerts its action by directly disrupting membranes of microorganisms. CecropinXJ had a small hemolytic effect on red blood cells even with a peptide concentration of 200 μM. Thus, cecropinXJ acts selectively on bacterial membranes. Purified recombinant antibacterial peptide, cecropinXJ, retained a high stability against E. coli ATCC25922 over a temperature range from 4 °C to 100 °C and a pH range from pH 2.0 to 12.0. Taken together, this study demonstrates that recombinant cecropinXJ can be produced in large quantities in yeast with genetic engineering methods, and that it has strong and rapid antimicrobial activities against all of microorganisms tested. Our results suggest that cecropinXJ is a potential candidate for therapy.

Expression systems for heterologous production of antimicrobial peptides

Antimicrobial peptides (AMPs) consist of molecules that act on the defense systems of numerous organisms toward multiple pathogens such as bacteria, fungi, parasites and viruses. These compounds have become extremely significant due to the increasing resistance of microorganisms to common antibiotics. However, the low quantity of peptides obtained from direct purification is, to date, still a remarkable bottleneck for scientific and industrial research development. Therefore, this review describes the main heterologous systems currently used for AMP production, including bacteria, fungi and plants, and also the related strategies for reaching greater functional peptide production. The main difficulties of each system are also described in order to provide some directions for AMP production. In summary, data revised here indicate that large-scale production of AMPs can be obtained using biotechnological tools, and the products may be applied in the pharmaceutical industry as well as in agribusiness.

Secretion and activity of antimicrobial peptide cecropin D expressed in Pichia pastoris

To express the antimicrobial peptide cecropin D in Pichia pastoris and determine the activity of the expressed product, four oligonucleotide fragments were synthesized in accordance with the available cecropin D sequences and a codon bias suitable for Pichia pastoris. Sequence fragments were phosphorylated, annealed, linked and cloned into the expression vector pGAPZαA and the yeast α-mating factor signal peptide was used as the signal sequence. The P. pastoris SMD1168 cells were transformed by electroporation using the constructed recombinant plasmid pGAPZαA-cecropin D. We were able to demonstrate by PCR that the cecropin D sequence had integrated into the P. pastoris genome. The expressed and secreted product was identified using Tricine-SDS-PAGE. Antibacterial activity was demonstrated using an agarose diffusion test and turbidimetry. The molecular mass of the recombinant cecropin D was estimated to be 3,900 Da. The recombinant cecropin D exhibited antibacterial activity for both Gram-positive and Gram-negative bacteria, suggesting that cecropin D was successfully expressed in P. pastoris. This approach holds great promise for antibacterial drug development.

Expression of 4kD scorpion defensin and its in vitro synergistic activity with conventional antibiotics

The 4kD scorpion defensin (SD) is a potent disulfide-linked peptide. In this study, we expressed it in methylotrophic yeast Pichia pastoris and purified it using Ni-NTA His Bind Resin. We investigated its in vitro antibacterial activity and effect in combination with several conventional antibiotics. We first examined its antibacterial activity towards several Gram-positive and Gram-negative bacteria. Then we used the broth microdilution method to test drugs alone and in combination and used the fractional inhibitory concentration (FIC index) to classify the drug interactions. Our study showed the expressed SD peptide has antibacterial activity against Salmonella typhimurium, E. coli and S. aureus etc. Synergy or additive interaction was observed between SD and Norfloxacin, Polymyxin B and Ampicillin. Cell growth tests showed that combination of SD and Norfloxacin can improve their activity against bacteria. This result maybe permit lower using of the conventional antibiotic agents more effectively and safely.

cDNA cloning and characterization of the antibacterial peptide cecropin 1 from the diamondback moth, Plutella xylostella L

Cecropins are linear cationic antibacterial peptides that have potent activities against microorganisms. In the present study, a 480bp full-length cDNA encoding diamondback moth (Plutella xylostella) cecropin 1 (designated as Px-cec1) was obtained using RT-PCR. A Northern blot analysis showed that the Px-cec1 transcript was predominantly expressed in fat bodies, hemocytes, midgut and epidermis with the highest expression level in fat bodies. The expression of Px-cec1 mRNA in fat bodies was significantly increased 24h after microbial challenge, with the highest induced expression by Staphylococcus aureus. A circular dichroism (CD) analysis revealed that the recombinant Px-cec1 mainly contained α-helixes. Antimicrobial assays demonstrated that recombinant Px-cec1 exhibited a broad spectrum of anti-microbial properties against fungi, Gram-positive and Gram-negative bacteria, but it did not exhibit hemolytic activity against human erythrocytes. Furthermore, Px-cec1 caused significant morphological alterations of S. aureus, as shown by scanning electron microscopy and transmission electron microscopy. These results demonstrated that Px-cec1 exerts its antibacterial activity by acting on the cell membrane to disrupt bacterial cell structures.

Production, purification, and characterization of the cecropin from Plutella xylostella, pxCECA1, using an intein-induced self-cleavable system in Escherichia coli

Antimicrobial peptides (AMPs) are widely expressed and play an important role in innate immune defense against infectious agents such as bacteria, viruses, fungi, and parasites. Cecropins are a family of AMPs synthesized in the fat body of insects that have proven effective at killing specific pathogens. In order to fulfill their clinical potential as antimicrobial drugs, a simple, cost-effective method to express AMPs is sorely needed. In this study, we expressed and characterized the cecropin from Plutella xylostella (pxCECA1) using an intein-dependent expression system in Escherichia coli. We cloned the pxCECA1 gene from larva by RT-PCR and fused the encoding sequence of mature pxCECA1 with an intein gene and a chitin-binding domain gene (CBD) in pTWIN1 plasmid. The fusion protein CBD-intein-pxCECA1 was expressed in E. coli BL21 (DE3) and separated by flowing cell extracts through a chitin column. Subsequently, self-cleavage of the intein at its C-terminus was induced in a temperature- and pH-dependent manner, resulting in the release of mature pxCECA1. The optimal conditions for self-cleavage were determined to be pH 6.0 for 48 h at 4°C, under which 12.3 mg of recombinant pxCECA1 could be recovered from 1 l of E. coli culture. The purified pxCECA1 displayed antimicrobial activity against a broad variety of gram-positive and gram-negative bacteria. This preparation was especially effective against Staphylococcus aureus, including methicillin-resistant strains. Catalase release assays demonstrated that pxCECA1 acts as a microbicidal agent. These results show for the first time that the IMPACT-TWIN expression system is an efficient, cost-effective way to produce fully functional AMPs and that the AMP pxCECA1 is a novel microbicidal agent with promising therapeutic applications.

Control of apple blue mold by Pichia pastoris recombinant strains expressing cecropin A

Recombinant Pichia pastoris yeasts expressing cecropin A (GS115/CEC), was evaluated for the control of the blue mold of apple caused by Penicillium expansum due to cecropin A peptide's effective antimicrobial effects on P. expansum spores by the thiazolyl blue (MTT) assay. Then, the protein concentration was determined and it was expressed at high levels up to 14.2 mg/L in the culture medium. Meanwhile, the population growth was assayed in vivo. The population growth of recombinant strain GS115/CEC was higher than that of non-transformed strain GS115 in red Fuji apples wounds. Recombinant yeast strains GS115/CEC significantly inhibited growth of germinated P. expansum spores in vitro and inhibited decay development caused by P. expansum in apple fruits in vivo when compared with apple fruits inoculated with sterile water or the yeast strain GS115/pPIC (plasmid pPIC9k transformed in GS115). This study demonstrated the potential of expression of the antifungal peptide in yeast for the control of postharvest blue mold infections on pome fruits.

Optimized production of scygonadin in Pichia pastoris and analysis of its antimicrobial and antiviral activities

The crab antimicrobial peptide scygonadin is confirmed to have antimicrobial activity against bacteria and it is probably associated with the reproductive immunity in Scylla paramamosain. To obtain large quantity of scygonadin for further biological assays, a 306 bp cDNA sequence encoding the mature peptide of scygonadin was cloned into a secretion vector of pPIC9K, and a high-level of the recombinant scygonadin was achieved in Pichia pastoris. The optimal expression condition was determined as incubation with 0.5% methanol for 48 h at 28 °C under pH 6.0, and a total of 70 mg scygonadin was expressed in 1L culture medium. The recombinant product was purified and 97% pure scygonadin was obtained using immobilized metal affinity chromatography with a yield of 46 mg/L. The recombinant scygonadin was confirmed using SDS-PAGE analysis and MS-fingerprinting. P. pastoris-derived scygonadin exhibited relatively higher antimicrobial activities against bacteria than Escherichia coli-derived scygonadin. The antimicrobial activity of the recombinant scygonadin against pathogenic Aeromonas hydrophila showed salt resistant and the killing kinetics of A. hydrophila was time dependent. Besides, the antiviral assay demonstrated that scygonadin could interfere with white spot syndrome virus (WSSV) replication in vitro-cultured crayfish haematopoietic (Hpt) cells. Taken together, this is the first report on the heterologous expression of scygonadin in P. pastoris, and P. pastoris is an effective expression system for producing large quantities of biological active scygonadin for both research and agricultural application.

Recombinant antimicrobial peptide hPAB-β expressed in Pichia pastoris, a potential agent active against methicillin-resistant Staphylococcus aureus

As a potential therapeutic agent, antimicrobial peptide has received increased attention in recent years. However, high-level expression of a small peptide with antimicrobial activity is still a challenging task. In this study, the coding sequence of antimicrobial peptide hPAB-β, a variant derived from human beta-defensin 2, was cloned into pPIC9K vector and transformed into Pichia pastoris. P. pastoris transformants harbored with multi-copy plasmids were screened by G418 selection. When the transformed cells were induced by methanol, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, Western blot, and matrix-assisted laser desorption ionization-time of flight mass spectrometry revealed recombinant hPAB-β products consisting of three protein species of 4,680.4, 4,485.3, and 4,881.9 Da at proportions of 58%, 36%, and 6%, respectively, which may be due to the incomplete processing of the fusion signal peptide of α-factor by the STE13 protease. Expressed hPAB-β was secreted into the culture medium at a level of 241.2 ± 29.5 mg/L. Purified hPAB-β with 95% homogeneity was obtained by 10 kDa membrane filtration followed by cation ion-exchange chromatography with a SP-Sepharose XL column. The two major protein species separated through a SOURCE 30RPC reverse phase chromatography column showed definite antimicrobial activities against Staphylococcus aureus. All 22 methicillin-resistant S. aureus (MRSA) isolates with multidrug resistance phenotype were sensitive to the recombinant hPAB-β with minimal inhibitory concentrations of 8-64 μg/ml. Our results show that the methylotrophic yeast-inducible system is suitable for high-level expression of active hPAB-β, and that expressed hPAB-β in P. pastoris may be a potential antimicrobial agent against MRSA infection.

Isolation, characterization and anti-cancer activity of SK84, a novel glycine-rich antimicrobial peptide from Drosophila virilis

We report herein the isolation and characterization of a novel glycine-rich antimicrobial peptide purified from the larvae of Drosophila virilis. A range of chromatographic methods was used for isolation and its antibacterial activity against Bacillus subtilis was employed to screen for the most active fractions. The peptide, termed SK84 due to its N-terminal serine, C-terminal lysine and a total of 84 residues, was completed sequenced using RT-PCR cDNA cloning. SK84 contains a high level of glycine (15.5%) and a hexaglycine cluster motif in the N-terminal part. SK84 displayed antibacterial activity against the tested Gram-positive bacteria (B. subtilis, Bacillus thuringiensis and Staphylococcus aureus), but had no effect on Gram-negative bacteria (Pseudomonas aeruginosa, Escherichia coli) and fungi (Saccharomyces cerevisiae, Candida albicans). SK84 had specific inhibitory effects on the proliferation of several cancer cell lines (Human leukemia THP-1, liver cancer HepG2, and breast cancer MCF-7 cells), but no hemolytic activity. The results from scanning electron microscopy observations revealed that SK84 killed THP-1 cells by destroying the cell membranes. Alignment results show that SK84 is a mature protein processed from the pseudoprotein GJ19999 from D. virilis, and is very similar to several pseudoproteins from different Drosophila species. Our results show that SK84 represents a novel glycine-rich peptide family in Drosophila species with antimicrobial and anti-cancer cell activities.

Novel expression vector for secretion of cecropin AD in Bacillus subtilis with enhanced antimicrobial activity

Cecropin AD, a chimeric antimicrobial peptide obtained from cecropins, is effective at killing specific microorganisms. However, a highly efficient expression system is still needed to allow for commercial application of cecropin AD. For the exogenous expression of cecropin AD, we fused the cecropin AD gene with a small ubiquitin-like modifier (SUMO) gene and a signal peptide of SacB, while a Bacillus subtilis expression system was constructed based on Bacillus subtilis cells genetically modified by the introduction of an operon including an isopropyl-beta-D-thiogalactopyranoside (IPTG)-inducible Spac promoter, a signal peptide of amyQ, and the SUMO protease gene. The recombinant cecropin AD was expressed, and 30.6 mg of pure recombinant protein was purified from 1 liter of culture supernatant. The purified cecropin AD displayed antimicrobial activity against some pathogens, such as Staphylococcus aureus and Escherichia coli, and was especially effective toward Staphylococcus aureus, with MICs of <0.05 microM (0.2 microg/ml). Stability analysis results showed that the activity of cecropin AD was not influenced by temperatures as high as 55 degrees C for 20 min; however, temperatures above 85 degrees C (for 20 min) decreased the antimicrobial activity of cecropin AD. Varying the pH from 4.0 to 9.0 did not appear to affect the activity of cecropin AD, but some loss of potency was observed at pH values lower than pH 4.0. Under the challenge of several proteases (proteinase K, trypsin, and pepsin), cecropin AD maintained functional activity. The results indicated that the recombinant product expressed by the designed Bacillus subtilis expression system was a potent antimicrobial agent and could be applied to control infectious diseases of farm animals or even humans.

Expression, purification and structural studies of a short antimicrobial peptide

We have produced a small antimicrobial peptide PFWRIRIRR in bacteria utilizing production in the form of insoluble fusion protein with ketosteroid isomerase. The recombinant peptide was rapidly and efficiently isolated by acidic cleavage of the fusion protein based on the acid labile Asp-Pro bond at the N-terminus of the peptide. The peptide has antibacterial activity and neutralizes macrophage activation by LPS. The selectivity of the peptide against bacteria correlates with preferential binding to acidic phospholipid vesicles. Solution structure of the peptide in SDS and DPC micelles was determined by NMR. The peptide adopts a well-defined structure, comprising a short helical segment. Cationic and hydrophobic clusters are segregated along the molecular axis of the short helix, which is positioned perpendicular to the membrane plane. The position of the helix is shifted in two micellar types and more nonpolar surface is exposed in anionic micelles. Overall structure explains the advantageous role of the N-terminal proline residue, which forms an integral part of the hydrophobic cluster.

High-level expression of active recombinant ubiquitin carboxyl-terminal hydrolase of Drosophila melanogaster in Pichia pastoris

Ubiquitin carboxyl-terminal hydrolases (UCHs) are implicated in the proteolytic processing of polymeric ubiquitin. The high specificity for the recognition site makes UCHs useful enzymes for in vitro cleavage of ubiquitin fusion proteins. In this work, an active C-terminal His-tagged UCH from Drosophila melanogaster (DmUCH) was produced as a secretory form in a recombinant strain of the methylotrophic yeast Pichia pastoris. The production of recombinant DmUCH by Mut^s strain was much higher than that by Mut⁺ strain, which was confirmed by Western blot analysis. When expression was induced at pH 6.0 in a BMMY/methanol medium, the concentration of recombinant DmUCH reached 210 mg l⁻¹. With the (His)₆-tag, the recombinant DmUCH was easily purified by Ni-NTA chromatography and 18 mg pure active DmUCH were obtained from 100 ml culture broth supernatant. Ubiquitin–magainin fusion protein was efficiently cleaved by DmUCH, yielding recombinant magainin with high antimicrobial activity. After removing the contaminants by Ni-NTA chromatography, recombinant magainin was purified to homogeneity easily by reversed-phase HPLC. Analysis of the recombinant magainin by ESI-MS showed that the molecular weight of the purified recombinant magainin was 2465 Da, which perfectly matches the mass calculated from the amino acid sequence. The result of mass spectrometry confirmed that the purified His-tagged DmUCH can recognize the ubiquitin–magainin fusion protein and cleave it at the carboxyl terminus of ubquitin precisely. Our results showed that P. pastoris is a robust system to express the secreted form of DmUCH.

Purification and characterization of a thermal stable antimicrobial protein from housefly larvae, Musca domestica, induced by ultrasonic wave

This work describes the induction, purification and partial biochemical characterizations of an antimicrobial protein from the housefly larvae induced by ultrasonic wave. It has been purified to apparent homogeneity by ammonium sulfate precipitation followed by Sephadex G-75, Bio-gel P6 gel filtration, and CM-Sepharose Fast Flow cation exchange chromatography. The protein is a cationic protein with an apparent molecular weight of 16315 Da determined by no-denaturing electrophoresis and SDS-PAGE, respectively. Biochemical profile assays show that this protein has good thermal stability, and repeatedly frozen and defrosted durability. The optimum pH for antimicrobial activity is around pH5. The antimicrobial range of the protein includes Gram-positive, Gram-negative bacteria and some fungi. Results of the membrane permeability assays suggest that the probable mode of action of this protein is membrane-disrupting mechanism.

Characterization and functional recovery of a novel antimicrobial peptide (CECdir-CECret) from inclusion bodies after expression in Escherichia coli

CECdir-CECret is a novel non-toxic doublet 8.5 kDa peptide representing the natural coding sequence of the antimicrobial peptide Cecropin A from Drosophila melanogaster fused in-frame to its own inverted version. Expression of this cloned doublet peptide in Escherichia coli, yielded peptides that were mostly packaged into inclusion bodies. The new molecule was purified, solubilized and refolded, through a standard guanidine-based procedure. The recovered refolded peptides were then characterized by HPLC chromatography, MALDI-TOF-mass spectrometry and peptide sequencing, and finally evaluated for their antimicrobial potential. The novel doublet peptide CECdir-CECret, displays an enhanced in vitro antimicrobial activity and action spectrum in comparison to the monomer Cecropin A.

Characterization and expression of a cecropin-like gene from Helicoverpa armigera

A cDNA encoding a cecropin-like antibacterial peptide was obtained by RT-PCR from cotton budworm (Helicoverpa armigera). The cloned cDNA consists of 773 nucleotides with a 192 bp open reading frame encoding a peptide of 63 aa, which is comprised of a 21 aa signal peptide and a 42 amino acids mature peptide. The amino acid sequence of the mature peptide is highly similar to those D-type cecropins. The peptide was named as HacD. RT-PCR revealed that the transcript of HacD gene was inducible and could be detected in fatbodies, midguts, hemocytes and Malpighian tubules. HacD was highly expressed in E. coli M15 by fusing with green fluorescent protein (GFP). After purification, desalting and cleavage with factor Xa, HacD was released and showed antibacterial activity to both Gram-positive and Gram-negative bacteria. The genomic DNA of HacD was amplified by TAIL-PCR. NF-kappaB and NF-IL6 binding sites were found in the 5'-upstream regulatory region of HacD gene. EMSA (electrophoretic mobility shift assay) revealed that nuclear proteins from the immunized larvae could bind to the NF-kappaB site, but no nuclear proteins were found to bind to the NF-IL6 site. It was proposed that the NF-kappaB site might contribute to the expression of HacD.

Expression and purification of a recombinant antibacterial peptide, cecropin, from Escherichia coli

Insect cecropins are small basic polypeptides synthesized in fat body and hemocytes in response to bacterial infections or hypodermic injuries. To explore a new approach for high expression of soluble cecropin in Escherichia coli cells, we fused the sequence encoding Musca domestica mature cecropin (named Mdmcec) in-frame to thioredoxin (TRX) gene to construct an expression vector pTRX-6His-Mdmcec. An enterokinase cleavage site was introduced between the 6xHis-tag and Mdmcec to facilitate final release of the recombinant Mdmcec. The fusion protein TRX-6His-Mdmcec was purified successfully by HisTrap HP affinity column and a high yield of 48.0mg purified fusion protein was obtained from 1L culture. Recombinant Mdmcec was readily obtained by enterokinase cleavage of the fusion protein followed by HPLC chromatography, and 11.2mg pure active recombinant Mdmcec was obtained from 1L E. coli culture. The molecular mass of recombinant Mdmcec determined by electrospray ionization-mass spectrometry (ESI-MS) is identical to that of native cecropin. Analysis of recombinant Mdmcec by circular dichroism (CD) indicated that recombinant Mdmcec contained predominantly alpha-helix with some random coil. Antimicrobial activity assays demonstrated that recombinant Mdmcec had a broad spectrum of activity against fungi, Gram-positive and negative bacteria. The procedure described in this study will provide a reliable and simple method for production of different cationic peptides for biological studies.

Expression of recombinant hybrid peptide cecropinA(1-8)-magainin2(1-12) in Pichia pastoris: purification and characterization

Hybrid antibacterial peptide CA-MA (cecropinA(1-8)-magainin2(1-12)) is a linear cationic peptide that has potent antimicrobial properties without hemolytic activity. To explore a new approach of expression of hybrid peptide CA-MA in methylotrophic yeast, Pichia pastoris, the gene of CA-MA was obtained by recursive PCR (rPCR) and cloned into the vector pPICZalpha-A. The SalI-linearized plasmid pPICZalpha-CA-MA was transformed into P. pastoris SMD1168 by electroporation. The expression was induced for 96h with 1.0% methanol at 28 degrees C, pH 5.0. Recombinant CA-MA was purified by reversed-phase HPLC and 22 mg pure active CA-MA was obtained from 1L fermentation culture. Tricine-SDS-PAGE indicated that recombinant CA-MA protein molecular weight is 2.6 kDa. Mass spectrometry of purified CA-MA demonstrated a single large signal for the molecular ion [M+2H+](2+) at 1281.07 m/z, identical to that of the putative protein (2.56 kDa). Antimicrobial assays showed that CA-MA has a broad spectrum of antimicrobial property against fungi, as well as Gram-positive and Gram-negative bacteria. This is the first report on the heterologous expression of a hybrid antibacterial peptide with molecular weight below 3.0 kDa in P. pastoris. Our results demonstrate that functional CA-MA can be produced in sufficient quantities using P. pastoris for use in further studies on functionality and diagnostic applications.