Permeabilizing action of an antimicrobial lactoferricin-derived peptide on bacterial and artificial membranes

AbstractA synthetic peptide (23 residues) that includes the antibacterial and lipopolysaccharide-binding regions of human lactoferricin, an antimicrobial sequence of lactoferrin, was used to study its action on cytoplasmic membrane of Escherichia coli 0111 and E. coli phospholipid vesicles. The peptide caused a depolarization of the bacterial cytoplasmic membrane, loss of the pH gradient, and a bactericidal effect on E. coli. Similarly, the binding of the peptide to liposomes dissipated previously created transmembrane electrical and pH gradients. The dramatic consequences of the transmembrane ion flux during the peptide exposure indicate that the adverse effect on bacterial cells occurs at the bacterial inner membrane

Structural analysis of APOB variants, p.(Arg3527Gln), p.(Arg1164Thr) and p.(Gln4494del), causing Familial Hypercholesterolaemia provides novel insights into variant pathogenicity

Free PMC Article: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4672294/Familial hypercholesterolaemia (FH) is an inherited autosomal dominant disorder resulting from defects in the low-density lipoprotein receptor (LDLR), in the apolipoprotein B (APOB) or in the proprotein convertase subtilisin/kexin type 9 (PCSK9) genes. In the majority of the cases FH is caused by mutations occurring within LDLR, while only few mutations in APOB and PCSK9 have been proved to cause disease. p.(Arg3527Gln) was the first mutation in APOB being identified and characterized. Recently two novel pathogenic APOB variants have been described: p.(Arg1164Thr) and p.(Gln4494del) showing impaired LDLR binding capacity, and diminished LDL uptake. The objective of this work was to analyse the structure of p.(Arg1164Thr) and p.(Gln4494del) variants to gain insight into their pathogenicity. Secondary structure of the human ApoB100 has been investigated by infrared spectroscopy (IR) and LDL particle size both by dynamic light scattering (DLS) and electron microscopy. The results show differences in secondary structure and/or in particle size of p.(Arg1164Thr) and p.(Gln4494del) variants compared with wild type. We conclude that these changes underlie the defective binding and uptake of p.(Arg1164Thr) and p.(Gln4494del) variants. Our study reveals that structural studies on pathogenic variants of APOB may provide very useful information to understand their role in FH disease

Bioprinting as a food production technique: Conceptual and ethical aspects, advantages and disadvantages, and applications

3D bioprinters present techniques that have various applications in the food industry. For this reason, this work aims to compile and review various research works focused on the utilities and advantages of this type of machinery. Where we first mention the basis of these bioprinting techniques and then proceed to highlight the bioethical issues that surround their application in the food industry, analyze the current advantages and disadvantages, the user that has been given in the production of food for astronauts, and also mention some of the research that has been taking place in Latin America and the world. The greatest advantage of 3D bioprinting of food is the speed of production compared to traditional manufacturing methods, allowing one to obtain food with various geometric shapes; it allows control of the nutritional value, and the texture of the product, reduces environmental pollution and has the advantage of being able to take advantage of the greater performance of the materials required for production. Additionally, this technology is considered an alternative production technique that will be used to solve the problem of feeding in places of scarce resources such as space and areas not suitable for animal husbandry

MLb-LDLr: A Machine Learning Model for Predicting the Pathogenicity of LDLr Missense Variants

Untreated familial hypercholesterolemia (FH) leads to atherosclerosis and early cardiovascular disease. Mutations in the low-density lipoprotein receptor (LDLr) gene constitute the major cause of FH, and the high number of mutations already described in the LDLr makes necessary cascade screening or in vitro functional characterization to provide a definitive diagnosis. Implementation of high-predicting capacity software constitutes a valuable approach for assessing pathogenicity of LDLr variants to help in the early diagnosis and management of FH disease. This work provides a reliable machine learning model to accurately predict the pathogenicity of LDLr missense variants with specificity of 92.5% and sensitivity of 91.6%. © 2021 The Author

E. coli a-hemolysin: a membrane-active protein toxin

Alpha-Hemolysin is synthesized as a 1024-amino acid polypeptide, then intracellularly activated by specific fatty acylation. A second activation step takes place in the extracellular medium through binding of Ca2+ ions. Even in the absence of fatty acids and Ca2+ HlyA is an amphipathic protein, with a tendency to self-aggregation. However, Ca2+-binding appears to expose hydrophobic patches on the protein surface, facilitating both self-aggregation and irreversible insertion into membranes. The protein may somehow bind membranes in the absence of divalent cations, but only when Ca2+ (or Sr2+, or Ba2+) is bound to the toxin in aqueous suspensions, i.e., prior to its interaction with bilayers, can <FONT FACE="Symbol">a</FONT>-hemolysin bind irreversibly model or cell membranes in such a way that the integrity of the membrane barrier is lost, and cell or vesicle leakage ensues. Leakage is not due to the formation of proteinaceous pores, but rather to the transient disruption of the bilayer, due to the protein insertion into the outer membrane monolayer, and subsequent perturbations in the bilayer lateral tension. Protein or glycoprotein receptors for <FONT FACE="Symbol">a</FONT>-hemolysin may exist on the cell surface, but the toxin is also active on pure lipid bilayers

Reversible adsorption and nonreversible insertion of Escherichia coli alpha-hemolysin into lipid bilayers.

Alpha-Hemolysin is an extracellular protein toxin (107 kDa) produced by some pathogenic strains of Escherichia coli. Although stable in aqueous medium, it can bind to lipid bilayers and produce membrane disruption in model and cell membranes. Previous studies had shown that toxin binding to the bilayer did not always lead to membrane lysis. In this paper, we find that alpha-hemolysin may bind the membranes in at least two ways, a reversible adsorption and an irreversible insertion. Reversibility is detected by the ability of liposome-bound toxin to induce hemolysis of added horse erythrocytes; insertion is accompanied by an increase in the protein intrinsic fluorescence. Toxin insertion does not necessarily lead to membrane lysis. Studies of alpha-hemolysin insertion into bilayers formed from a variety of single phospholipids, or binary mixtures of phospholipids, or of phospholipid and cholesterol, reveal that irreversible insertion is favored by fluid over gel states, by low over high cholesterol concentrations, by disordered liquid phases over gel or ordered liquid phases, and by gel over ordered liquid phases. These results are relevant to the mechanism of action of alpha-hemolysin and provide new insights into the membrane insertion of large proteins