Production and isotope labeling of antimicrobial peptides in Escherichia coli by means of a novel fusion partner that enables high-yield insoluble expression and fast purification.
ABSTRACT A method is presented that allows efficient production of antimicrobial peptides in bacteria by means of fusion to the histone fold domain of the human transcription factor TAF12. This small fusion partner drives high-level expression of peptides and leads to their accumulation in an entirely insoluble form, thereby eliminating toxicity to the host. Using the antimicrobial peptide LAH4 as an example, we demonstrate that neither affinity purification of the TAF12 fusion protein nor initial solubilization of inclusion bodies in denaturing buffers is required. Instead, crude insoluble material from bacteria is directly dissolved in formic acid for immediate release of the peptide through chemical cleavage at a unique Asp-Pro site. This is followed by purification to homogeneity in a single chromatographic step. Because of the elevated expression levels of the histone fold domain and its small size (8 kDa), this straightforward purification scheme produces yields in excess of 10 mg active peptide per liter of culture. We demonstrate that TAF12 fusion allows expression of a wide range of antimicrobial peptides as well as efficient isotope labeling for NMR studies.
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ABSTRACT: Previously, we found that baculoviral polyhedrin (Polh) can successfully be used in Escherichia coli as a fusion partner for the expression of special foreign proteins as inclusion bodies, and the resulting, easily isolatable Polh-induced fusion inclusion bodies had almost the same characteristics as the native Polh. Here, we investigated the effects of co-expression of baculoviral FP25 protein on Polh-induced inclusion-body production in an E. coli expression system, as FP25 is known to be involved specifically in polyhedra formation. Using several analytical tools, including SDS-PAGE, pronase proteolysis, solubilization under alkaline conditions, and electron microscopy, we found that co-expressed FP25 was associated with Polh-induced inclusion bodies and that its co-expression led to formation of compact inclusion bodies as well as high production levels. We confirmed that FP25 co-expression induced higher production levels of other heterologous protein, antimicrobial peptide Hal18, fused with aggregation-prone Polh. Therefore, co-expression of baculoviral FP25 can be promisingly used to increase the levels of baculoviral Polh-fused foreign proteins, especially harmful proteins, expressed as inclusion bodies in an E. coli expression system.Biotechnology and Bioengineering 05/2007; 96(6):1183-90. · 3.65 Impact Factor
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ABSTRACT: Several fusion strategies have been developed for the expression and purification of small antimicrobial peptides (AMPs) in recombinant bacterial expression systems. However, some of these efforts have been limited by product toxicity to host cells, product proteolysis, low expression levels, poor recovery yields, and sometimes an absence of posttranslational modifications required for biological activity. For the present work, we investigated the use of the baculoviral polyhedrin (Polh) protein as a novel fusion partner for the production of a model AMP (halocidin 18-amino-acid subunit; Hal18) in Escherichia coli. The useful solubility properties of Polh as a fusion partner facilitated the expression of the Polh-Hal18 fusion protein ( approximately 33.6 kDa) by forming insoluble inclusion bodies in E. coli which could easily be purified by inclusion body isolation and affinity purification using the fused hexahistidine tag. The recombinant Hal18 AMP ( approximately 2 kDa) could then be cleaved with hydroxylamine from the fusion protein and easily recovered by simple dialysis and centrifugation. This was facilitated by the fact that Polh was soluble during the alkaline cleavage reaction but became insoluble during dialysis at a neutral pH. Reverse-phase high-performance liquid chromatography was used to further purify the separated recombinant Hal18, giving a final yield of 30% with >90% purity. Importantly, recombinant and synthetic Hal18 peptides showed nearly identical antimicrobial activities against E. coli and Staphylococcus aureus, which were used as representative gram-negative and gram-positive bacteria, respectively. These results demonstrate that baculoviral Polh can provide an efficient and facile platform for the production or functional study of target AMPs.Applied and Environmental Microbiology 10/2005; 71(9):5038-43. · 3.68 Impact Factor
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ABSTRACT: MGD-1 is a 39-residue defensin-like peptide isolated from the edible Mediterranean mussel, Mytilus galloprovincialis. This peptide is characterized by the presence of four disulfide bonds. We report here its solid-phase synthesis and an easy way to improve the yield of the four native disulfide bonds. Synthetic and native MGD-1 display similar antibacterial activity, suggesting that the hydroxylation of Trp28 observed in native MGD-1 is not involved in the antimicrobial effect. The three-dimensional solution structure of MGD-1 has been established using (1)H NMR and mainly consists of a helical part (Asn7-Ser16) and two antiparallel beta-strands (Arg20-Cys25 and Cys33-Arg37), together giving rise to the common cystine-stabilized alpha-beta motif frequently observed in scorpion toxins. In MGD-1, the cystine-stabilized alpha-beta motif is stabilized by four disulfide bonds (Cys4-Cys25, Cys10-Cys33, Cys14-Cys35, and Cys21-Cys38), instead of by the three disulfide bonds commonly found in arthropod defensins. Except for the Cys21-Cys38 disulfide bond which is solvent-exposed, the three others belong to the particularly hydrophobic core of the highly constrained structure. Moreover, the C4-P5 amide bond in the cis conformation characterizes the MGD-1 structure. MGD-1 and insect defensin A possess similar bactericidal anti-Gram-positive activity, suggesting that the fourth disulfide bond of MGD-1 is not essential for the biological activity. In agreement with the general features of antibacterial peptides, the MGD-1 and defensin A structures display a typical distribution of positively charged and hydrophobic side chains. The positively charged residues of MGD-1 are located in three clusters. For these two defensin peptides isolated from insects and mollusks, it appears that the rather well conserved location of certain positively charged residues and of the large hydrophobic cluster are enough to generate the bactericidal potency and the Gram-positive specificity.Biochemistry 01/2000; 39(47):14436-14447. · 3.38 Impact Factor