Molecular Dynamics Simulations Help Determine the Molecular Mechanisms of Lasioglossin-III and Its Variant Peptides' Membrane Interfacial Interactions

Lasioglossin-III (LL-III) is a potent broad-spectrum antimicrobial peptide used in diverse antimicrobial applications. In this work, coarse-grained and all-atom molecular dynamics simulation strategies were used in tandem to interpret the molecular mechanisms involved in the interfacial dynamics of LL-III and its recombinant variants during interactions with diverse cell membrane systems. Our results indicate that the membrane charges act as the driving force for initiating the membrane-peptide interactions, while the hydrophobic or van der Waals forces help to reinforce the membrane-peptide bindings. The optimized charge-hydrophobicity ratio of the LL-III peptides helps ensure their high specificity toward bacterial membranes compared to mammalian membrane systems, which also helps explain our experimental observations. Overall, we hope that our work gives new insight into the antimicrobial action of LL-III peptides and that the adopted simulation strategy will help other scientists and engineers extract maximal information from complex molecular simulations using minimal computational power.

Semi-Biosynthetic Production of Surface-Binding Adhesive Antimicrobial Peptides Using Intein-Mediated Protein Ligation

Microbial infections remain a global health concern, calling for the urgent need to implement effective prevention measures. Antimicrobial peptides (AMPs) have been extensively studied as potential antimicrobial coating agents. However, an efficient and economical method for AMP production is lacking. Here, we synthesized the direct coating adhesive AMP, NKC-DOPA5, composed of NKC, a potent AMP, and repeats of the adhesive amino acid 3,4-dihydroxyphenylalanine (DOPA) via an intein-mediated protein ligation strategy. NKC was expressed as a soluble fusion protein His-NKC-GyrA (HNG) in Escherichia coli, comprising an N-terminal 6× His-tag and a C-terminal Mxe GyrA intein. The HNG protein was efficiently produced in a 500-L fermenter, with a titer of 1.63 g/L. The NKC-thioester was released from the purified HNG fusion protein by thiol attack and subsequently ligated with chemically synthesized Cys-DOPA5. The ligated peptide His-NKC-Cys-DOPA5 was obtained at a yield of 88.7%. The purified His-NKC-Cys-DOPA5 possessed surface-binding and antimicrobial properties identical to those of the peptide obtained via solid-phase peptide synthesis. His-NKC-Cys-DOPA5 can be applied as a practical and functional antimicrobial coating to various materials, such as medical devices and home appliances.

Elastin-like Polypeptides in Development of Nanomaterials for Application in the Medical Field

Elastin-like polypeptides (ELPs) are biopolymers formed by amino acid sequences derived from tropoelastin. These biomolecules can be soluble below critical temperatures, forming aggregates at higher temperatures, which makes them an interesting source for the design of different nanobiomaterials. These nanobiomaterials can be obtained from heterologous expression in several organisms such as bacteria, fungi, and plants. Thanks to the many advantages of ELPs, they have been used in the biomedical field to develop nanoparticles, nanofibers, and nanocomposites. These nanostructures can be used in multiple applications such as drug delivery systems, treatments of type 2 diabetes, cardiovascular diseases, tissue repair, and cancer therapy. Thus, this review aims to shed some light on the main advances in elastin-like-based nanomaterials, their possible expression forms, and importance to the medical field.

Production of antimicrobial peptide arasin-like Sp in Escherichia coli via an ELP-intein self-cleavage system

Antibiotic resistance is a major public health threat to both humans and animals. There is an urgent need for antimicrobial agents with novel modes of action. Antimicrobial peptides (AMPs) with broad-spectrum antimicrobial activity become the ideal alternative to traditional antibiotics. Here, the ELP-intein self-cleavage system was used to produce antimicrobial peptide arasin-likeSp in Escherichia coli. The tagged target protein (ELP-intein-arasin-likeSp) was mainly expressed in soluble, separated from cell lysates by the inverse transition cycling (ITC), and the arasin-likeSp was further purified by the self-cleavage of intein and the second round of ITC. The final yield of arasin-likeSp was about 3.56 mg/L. Purified arasin-likeSp exhibited significant antibacterial activities against the Gram-positive Bacillus subtilis and Gram-negative Vibrio harveyi bacteria. FE-SEM and PI staining analysis revealed that the arasin-likeSp treatment altered the morphology and membrane permeability of Bacillus subtilis and Vibrio harveyi. Collectively, these data suggest that arasin-likeSp is a candidate AMP for effective inhibition of Vibrio harveyi, a significant bacterial pathogen infecting marine fish and invertebrates. The ELP-intein self-cleavage system described here is a low-cost, simple and potential method for producing antimicrobial peptides, which lays foundations for the large-scale production of antimicrobial peptides in the future.

Production of a polar fish antimicrobial peptide in Escherichia coli using an ELP-intein tag

An important aspect related to infectious pathogens is their exceptional adaptability in developing resistance, which leads to a perpetual challenge in the discovery of antimicrobial drugs with novel mechanisms of action. Among them, antimicrobial peptides (AMPs) stand out as promising anti-infective molecules. In order to overcome the high costs associated with isolation from natural sources or chemical synthesis of AMPs we propose the expression of Pa-MAP 2, a polyalanine AMP. Pa-MAP 2 was fused to an ELP-intein tag where the ELP (Elastin-like polypeptide) was used to promote aggregation and fast and cost-effective isolation after expression, and the intein was used to stimulate a controlled AMP release. For these, the vector pET21a was used to produce Pa-MAP 2 fused to the N-termini region of a modified Mxe GyrA intein followed by 60 repetitions of ELP. Purified Pa-MAP 2 showed a MIC of 25μM against E. coli ATCC 8739. Batch fermentation demonstrated that Pa-MAP-2 can be produced in both rich and defined media at yields 50-fold higher than reported for other AMPs produced by the ELP-intein system, and in comparable yields to expression systems with protease or chemical cleavage.

Rational Design of a Carrier Protein for the Production of Recombinant Toxic Peptides in Escherichia coli

Commercial uses of bioactive peptides require low cost, effective methods for their production. We developed a new carrier protein for high yield production of recombinant peptides in Escherichia coli very well suited for the production of toxic peptides like antimicrobial peptides. GKY20, a short antimicrobial peptide derived from the C-terminus of human thrombin, was fused to the C-terminus of Onconase, a small ribonuclease (104 amino acids), which efficiently drove the peptide into inclusion bodies with very high expression levels (about 200-250 mg/L). After purification of the fusion protein by immobilized metal ion affinity chromatography, peptide was obtained by chemical cleavage in diluted acetic acid of an acid labile Asp-Pro sequence with more than 95% efficiency. To improve peptide purification, Onconase was mutated to eliminate all acid labile sequences thus reducing the release of unwanted peptides during the acid cleavage. Mutations were chosen to preserve the differential solubility of Onconase as function of pH, which allows its selective precipitation at neutral pH after the cleavage. The improved carrier allowed the production of 15-18 mg of recombinant peptide per liter of culture with 96-98% purity without the need of further chromatographic steps after the acid cleavage. The antimicrobial activity of the recombinant peptide, with an additional proline at the N-terminus, was tested on Gram-negative and Gram-positive strains and was found to be identical to that measured for synthetic GKY20. This finding suggests that N-terminal proline residue does not change the antimicrobial properties of recombinant (P)GKY20. The improved carrier, which does not contain cysteine and methionine residues, Asp-Pro and Asn-Gly sequences, is well suited for the production of peptides using any of the most popular chemical cleavage methods.