Lipopolysaccharide neutralization by the antibacterial peptide CM4.

Lipopolysaccharide (LPS) is a major constituent of the outer membrane of Gram-negative bacteria. Binding of LPS to the CD14+ murine macrophage cell line RAW264.7 results in pro-inflammatory cytokine secretion. In extreme cases, it leads to septic shock in vivo. Therefore, the pursuit for molecules with antiendotoxin properties is urgent. In this study, we investigated the efficacy of antibacterial peptide CM4 in binding Escherichia coli LPS in vitro. CM4 avidly bound to E. coli LPS, as proven by the limulus amoebocyte lysate assay. Furthermore, the killing activity of CM4 against E. coli was progressively inhibited by increasing concentrations of LPS added to the medium, further confirming the peptide's affinity for endotoxin. Flow cytometric analysis revealed that CM4 inhibited the binding of FITC-conjugated LPS to RAW264.7 cells. Likewise, the inhibition of peptide to LPS-dependent cytokine induction was analyzed. CM4 suppressed LPS-induced TNF-alpha and IL-6 mRNA expression and blocked release of TNF-alpha and NO following LPS challenge in RAW264.7 cells. Together these observations indicate that antibacterial peptide CM4 probably exerts protective actions against endotoxin shock by blocking the binding of LPS to CD14+ cells.

Expression, purification and characterization of anti-BAFF antibody secreted from the yeast Pichia pastoris.

B-Cell activating factor (BAFF) is critical for B cell survival and maturation; excessive expression of it corrupts B-cell tolerance and may lead to autoimmunity. The gene, scFv-Fc, coding for the antibody of BAFF was inserted into the eukaryotic expression vector, pPICZalphaA, and transformed into Pichia pastoris. A high-level expression strain was obtained using a 'yeastern blotting' method. The scFv-Fc antibody was purified and 56 mg was obtained from 1 l of culture supernatant. It retained high binding activity to both soluble BAFF and membrane-bound BAFF.

Expression of a cytotoxic cationic antibacterial peptide in Escherichia coli using two fusion partners.

It has been reported that it is difficult to express cationic antibacterial peptides in engineered bacteria because such peptides are highly toxic to the host bacteria cells and sensitive to intracellular proteases. Antibacterial peptide CM4 (ABP-CM4) is a small cationic peptide with broad-spectrum activities against bacteria, fungi and tumor cells, which may possibly be used as an antimicrobial agent. Here we tried to express ABP-CM4 in Escherichia coli cells using either the GST fusion system or the intein-mediated fusion expression system. In order to investigate the possible use of these two fusion partners in cationic small peptide expression and purification, a mutant ABP-CMt, which is a highly positively charged peptide with +9 charges at neutral pH, was designed. In the present study, we have shown that both ABP-CM4 and ABP-CMt peptides can be expressed and purified by the intein-mediated expression system but not by the GST fusion expression system. Thus the intein-mediated peptide expression and purification system potentially could be employed for the production of recombinant protease-sensitive and cytotoxic peptides.

[Expression of the antibacterial peptide CM4-like gene of Chinese silkworm Bombyx mori in Escherichia coli and its antibacterial activity analysis].

According to the amino acid sequence of CM4 and the bias for preferred condons of E. coli, the CM4-like gene was obtained by a recursive PCR (rPCR) strategy using two lapping oligonucleotides. The synthesized gene was coloned into the expression vector pET32(a) and transformed into E. coli BL21 (DE3). Recombinant CM4-like gene expression was driven by the T7 promoter on the vector upon addition of IPTG and high level of expression was achieved. The solube protein was purified by Ni-chelating agarose and treated with formic acid. After cleavege, the recombinant peptide was purified by another Ni(2+)-NTA-Agarose affinity chromatography and cation-exchange chromatography. Results of agarose diffuse assay and liquid turbidity analysis indicated that the recombinant peptide exhibited the antibacterial activity.

Molecular cloning, in vitro expression and bioactivity of goose B-cell activating factor.

B-cell activating factor (BAFF), belonging to the TNF family, is critical for B cell survival and maturation. cDNA of goose BAFF (gBAFF) was amplified from goose spleen by RT-PCR. The open reading frame (ORF) of gBAFF encodes a protein of 288-amino acid. The gBAFF shows 98, 92, 44 and 55% amino acid sequence identity with duck (dBAFF), chicken (cBAFF), mouse (mBAFF) and human BAFF (hBAFF), respectively. RT-PCR results showed that gBAFF mRNA is expressed in thymus and more highly expressed in the bursa of Fabricius and spleen. Recombinant soluble gBAFF (gsBAFF) expressed in Escherichia coli has molecular weight of approximately 19kDa. In vitro, purified gsBAFF was able to promote bursa B cells survival/proliferation in goose, duck and chicken. Furthermore, recombinant dsBAFF and csBAFF have a positive effect on goose, duck and chicken bursa B cells survival/proliferation. These findings indicate that gBAFF plays an important role in the survival/proliferation of goose B cells and, owing to its high evolutionary conservation, functional cross-reactivity exists between chicken, duck and goose BAFF.

Expression in Escherichia coli and purification of bioactive antibacterial peptide ABP-CM4 from the Chinese silk worm, Bombyx mori.

The antibacterial peptide CM4 (ABP-CM4), isolated from Chinese Bombys mori, is a 35-residue cationic, amphipathic alpha-helical peptide that exhibits a broad range of antimicrobial activity. To explore a new approach for the expression of ABP-CM4 in E. coli, the gene ABP-CM4, obtained by recursive PCR (rPCR), was cloned into the vector pET32a to construct a fusion expression plasmid. The fusion protein Trx-CM4 was expressed in soluble form, purified by Ni(2+)-chelating chromatography, and cleaved by formic acid to release recombinant CM4. Purification of rCM4 was achieved by affinity chromatography and reverse-phase HPLC. The purified of recombinant peptide showed antimicrobial activities against E. coli K(12)D(31), Penicillium chrysogenum, Aspergillus niger and Gibberella saubinetii. According to the antimicrobial peptide database (http://aps.unmc.edu/AP/main.html), 116 peptides contain a Met residue, but only 5 peptides contain the AspPro site, indicating a broader application of formic acid than CNBr in cleaving fusion protein. The successful application to the expression of the ABP-CM4 indicates that the system is a low-cost, efficient way of producting milligram quantities of ABP-CM4 that is biologically active.