Semenogelins Armed in Zn(II) and Cu(II): May Bioinorganic Chemistry Help Nature to Cope with Enterococcus faecalis?

Proteolytic degradation of semenogelins, the most abundant proteins from human semen, results in the formation of 26- and 29-amino acid peptides (SgIIA and SgI-29, respectively), which share a common 15 amino acid fragment (Sg-15). All three ligands are effective Zn(II) and Cu(II) binders; in solution, a variety of differently metalated species exist in equilibrium, with the [NH2, 3Nim] donor set prevailing at physiological pH in the case of both metals. For the first time, the Cu(II)-induced antimicrobial activity of Sg-15 against Enterococcus faecalis is shown. In the case of the two native semenogelin fragment metal complexes, the strong local positive charge in the metal-bound HH motif correlates well with their antimicrobial activity. A careful analysis of semenogelins' metal coordination behavior reveals two facts: (i) The histamine-like Cu(II) binding mode of SgI-29 strongly increases the stability of such a complex below pH 6 (with respect to the non-histamine-like binding of SgIIA), while in the case of the SgI-29 Zn(II)-histamine-like species, the stability enhancement is less pronounced. (ii) The HH sequence is a more tempting site for Cu(II) ions than the HXH one.

Zn(II) binding to pramlintide results in a structural kink, fibril formation and antifungal activity.

The antimicrobial properties of amylin, a 37-amino acid peptide hormone, co-secreted with insulin from the pancreas, are far less known than its antidiabetic function. We provide insight into the bioinorganic chemistry of amylin analogues, showing that the coordination of zinc(II) enhances the antifungal properties of pramlintide, a non-fibrillating therapeutic analogue of amylin. Zinc binds to the N-terminal amino group and His18 imidazole, inducing a kink in the peptide structure, which, in turn, triggers a fibrillization process of the complex, resulting in an amyloid structure most likely responsible for the disruption of the fungal cell.

Thermodynamic surprises of Cu(II)-amylin analogue complexes in membrane mimicking solutions.

Membrane environment often has an important effect on the structure, and therefore also on the coordination mode of biologically relevant metal ions. This is also true in the case of Cu(II) coordination to amylin analogues-rat amylin, amylin1-19, pramlintide and Ac-pramlintide, which offer N-terminal amine groups and/or histidine imidazoles as copper(II) anchoring sites. Complex stabilities are comparable, with the exception of the very stable Cu(II)-amylin1-19, which proves that the presence of the amylin C-terminus lowers its affinity for copper(II); although not directly involved, its appropriate arrangement sterically prevents early metal binding. Most interestingly, in membrane-mimicking solution, the Cu(II) affinities of amylin analogues are lower than the ones in water, probably due to the crowding effect of the membrane solution and the fact that amide coordination occurs at higher pH, which happens most likely because the α-helical structure, imposed by the membrane-mimicking solvent, prevents the amides from binding at lower pH, requiring a local unwinding of the α-helix.

Metal Complexation Mechanisms of Polyphenols Associated to Alzheimer's Disease.

Polyphenols are a class of compounds, produced by plants, which share the ability to act as potent antioxidants. First investigations on polyphenols' antioxidant activity are dated almost twenty years ago when their relationship and implication with the prevention and treatment of cancer was proposed for the first time. Later, in the early 2000s, the neuroprotective effects of several polyphenols were demonstrated. Nowadays, the benefits of a plethora of polyphenols have been studied and their ameliorating effects in several disease conditions, like cancer, cardiac and neuronal diseases are widely recognised. More than 1000 papers dealing with polyphenols and Alzheimer's disease have been published so far, describing the antioxidant properties, the metal chelating features and the anti-aggregating behavior of these compounds. The aim of this review is to rationalize, from a chemical point of view, the metal complexation mechanisms of polyphenols related to two significant events of Alzheimer's disease: oxidative stress and metal ion dyshomeostasis. In order to address this issue, we have herein discussed several aspects implicated in Alzheimer's disease and polyphenols involved in the treatment of the disease.

Zn(II)-alloferon complexes - Similar sequence, different coordination modes, no antibacterial activity.

Often, in the search for a highly defined scientific phenomenon, a different one becomes apparent. This was also the case of this work, in the scope of which we planned to search for metal-enhanced, novel antibacterial/antifungal compounds. Instead, we denied the existence of such and revealed the details of the bioinorganic chemistry of Zn(II)-alloferon complexes. Zinc(II) complexes of alloferon 1 and 2, ligands with a sequential difference of one amino acid only, show a substantially different coordination pattern at physiological pH. In the case of Zn(II)-alloferon 1 species, a histamine-like binding mode is observed (N-terminal amine and imidazole of His-1) and the coordination sphere is completed with the imidazole nitrogens of His-6 and His-9; His-12 is not involved in binding. In the case of Zn(II)-alloferon 2, the N-terminal amine and all the three imidazoles present in the sequence participate in the coordination, however, with the chemical shift of His-5 being less affected than those of other imidazoles. The histamine-like binding in Zn(II)-alloferon 1 complex strongly enhances its thermodynamic stability in comparison to the His-1 lacking alloferon 2 analogue. Despite previous reports on the antibacterial and antifungal activity of alloferon 1, no such activity was detected, neither for alloferon 1 and 2 nor for their Zn(II) complexes.

Zinc(II)-The Overlooked Éminence Grise of Chloroquine's Fight against COVID-19?

Zn(II) is an inhibitor of SARS-CoV-2's RNA-dependent RNA polymerase, and chloroquine and hydroxychloroquine are Zn(II) ionophores-this statement gives a curious mind a lot to think about. We show results of the first clinical trials on chloroquine (CQ) and hydroxychloroquine (HCQ) in the treatment of COVID-19, as well as earlier reports on the anticoronaviral properties of these two compounds and of Zn(II) itself. Other FDA-approved Zn(II) ionophores are given a decent amount of attention and are thought of as possible COVID-19 therapeutics.

Copper(II) and Amylin Analogues: A Complicated Relationship.

Protein aggregation has attracted substantial interest because of its role in causing many serious illnesses, such as neurodegenerative diseases and type II diabetes. Recent studies have shown that protein aggregation can be prevented by forming metal ion complexes with a target protein, which affects their conformation in solution and their physical properties, such as aggregation. Thus, understanding the interactions between aggregating molecules and bioactive metal ions such as Cu2+ is beneficial for new drug discovery. Pramlintide, a synthetic peptide drug, and its natural counterpart rat amylin are known to be resistant to aggregation because of the presence of proline residues, which are usually ß-sheet "breakers" within their amino acid sequence. Here, we investigate the Cu2+ coordination properties of pramlintide and rat amylin using nuclear magnetic resonance, circular dichroism, electron paramagnetic resonance, ultraviolet-visible spectroscopy, potentiometry, and mass spectrometry. We test the influence of Cu2+ on the aggregation properties of these amylin analogues with thioflavin T assays. We find that both peptides form stable complexes with Cu2+ with similar affinities at a 1:1 ratio. The N-termini of both peptides are involved in Cu2+ binding; His18 imidazole is an equally attractive binding site in the case of pramlintide. Our results show that Cu2+ ions influence the aggregation of pramlintide, but not that of rat amylin.

Bioinorganic chemistry of calcitermin - the picklock of its antimicrobial activity.

Calcitermin, an antimicrobial peptide from the fluid of the human airways, is a well-conserved, 15 amino acid C-terminal cleavage fragment of calgranulin C (VAIALKAAHYHTHKE), which is active under acidic pH conditions (pH 5.4). In an attempt to understand the impact of the coordination of Zn(ii) and Cu(ii) on the biological activity of calcitermin, we mutated each of the histidines with an alanine and studied the thermodynamics, binding mode and antimicrobial activity of wild type calcitermin and its H9A, H11A and H13A mutants and their Zn(ii) and Cu(ii) complexes. Both metals strongly enhance the antimicrobial activity of calcitermin-like peptides, although the link between the minimal inhibitory concentration (MIC) values and the stability, charge or structure of the complexes is not so obvious. As expected, the increase in the number of histidines makes the coordination of both metals more effective. There is no preferred Cu(ii) binding site in calcitermin: the stabilities of the Cu(ii)-H9A and Cu(ii)-H13A complexes are almost identical, while the Cu(ii)-H11A complex (in which two histidines are separated by three amino acids and only one His residue is involved in binding) is less stable. On the other hand, the higher stability of the Zn(ii)-H13A complex with respect to those formed by H9A and H11A suggests a pivotal role of His9 and His11 in Zn(ii) complexation. Impressive MIC breakpoints were obtained, similar and lower than those for commonly used antimicrobial agents that treat Candida albicans (Zn(ii) and Cu(ii) complexes of WT calcitermin and H9A, as well as H9A alone), Enterococcus faecalis (H11A, H13A and their metal complexes) and Staphylococcus aureus (H13A and its complexes).

Pneumococcal histidine triads - involved not only in Zn2+, but also Ni2+ binding?

Polyhistidine triad proteins, which participate in Zn2+ uptake in Streptococcus pneumoniae, contain multiple copies of the HxxHxH (histidine triad motif) sequence. We focus on three such motifs from one of the most common and well-conserved polyhistidine triad proteins, PhtA, in order to understand their bioinorganic chemistry; particular focus is given to (i) understanding which of the PhtA triads binds Zn2+ with the highest affinity (and why) and (ii) explaining whether Ni2+ (also crucial for bacterial survival and virulence) could potentially outcompete Zn2+ at its native binding site. There is no significant difference in the stability of zinc(ii) complexes with the three studied protein fragments, but one of the nickel(ii)-polyhistidine triads is remarkably stable; we explain why and hypothesize about the biological importance of this finding.

Anticancer properties of peptide fragments of hair proteins.

The primary function of hair and fur covering mammalian skin is to provide mechanical and thermal protection for the body. The proteins that constitute hair are extremely resistant to degradation by environmental factors. However, even durable materials can be slowly broken down by mechanical stresses, biodegradation mediated by endogenous enzymes in the skin or host microbes. We hypothesised that the biodegradation products of hair may possess bioprotective properties, which supplement their physical protective properties. Although evolutionary processes have led to a reduction in the amount of hair on the human body, it is possible that the bioprotective properties of hair biodegradation products have persisted. The human skin is exposed to various environmental carcinogenic factors. Therefore, we hypothesised that the potential bioprotective mechanisms of hair degradation products affect melanoma growth. We used pepsin to partially digest hair enzymatically, and this process produced a water-soluble lysate containing a mixture of peptides, including fragments of keratin and keratin-associated proteins. We found out that the mixtures of soluble peptides obtained from human hair inhibited the proliferation of human melanoma cells in vitro. Moreover, the hair-derived peptide mixtures also inhibited the proliferation of B lymphoma cells and urinary bladder cancer cells. Normal human cells varied in their susceptibility to the effects of the lysate; the hair-derived peptide mixtures modulated the proliferation of normal human fibroblasts but did not inhibit the proliferation of human mesenchymal cells derived from umbilical cord stromal cells. These results suggest that hair-derived peptides may represent a new class of anti-proliferative factors derived from basically structural proteins. Identification of active regulatory compounds and recognition of the mechanism of their action might pave the way to elaboration of new anticancer drugs.

Identification of a ferritin-like protein of Listeria monocytogenes as a mediator of ß-lactam tolerance and innate resistance to cephalosporins.

BACKGROUND: The food-borne pathogen Listeria monocytogenes is the causative agent of listeriosis. The ß-lactam antibiotics penicillin G and ampicillin are the current drugs of choice for the treatment of listerial infections. While isolates of L. monocytogenes are susceptible to these antibiotics, their action is only bacteriostatic and consequently, this bacterium is regarded as tolerant to ß-lactams. In addition, L. monocytogenes has a high level of innate resistance to the cephalosporin family of ß-lactams frequently used to treat sepsis of unknown etiology. Given the high mortality rate of listeriosis despite rational antibiotic therapy, it is important to identify genes that play a role in the susceptibility and tolerance of L. monocytogenes to ß-lactams. RESULTS: The hly-based promoter trap system was applied to identify penicillin G-inducible genes of L. monocytogenes. The results of reporter system studies, verified by transcriptional analysis, identified ten penicillin G-inducible genes. The contribution of three of these genes, encoding a ferritin-like protein (fri), a two-component phosphate-response regulator (phoP) and an AraC/XylS family transcriptional regulator (axyR), to the susceptibility and tolerance of L. monocytogenes to ß-lactams was examined by analysis of nonpolar deletion mutants. The absence of PhoP or AxyR resulted in more rapid growth of the strains in the presence of sublethal concentration of ß-lactams, but had no effect on the MIC values or the ability to survive a lethal dose of these antibiotics. However, the Δfri strain showed impaired growth in the presence of sublethal concentrations of penicillin G and ampicillin and a significantly reduced ability to survive lethal concentrations of these ß-lactams. A lack of Fri also caused a 2-fold increase in the sensitivity of L. monocytogenes to cefalotin and cephradine. CONCLUSIONS: The present study has identified Fri as an important mediator of ß-lactam tolerance and innate resistance to cephalosporins in L. monocytogenes. PhoP and AxyR are probably involved in transmitting signals to adjust the rate of growth of L. monocytogenes under ß-lactam pressure, but these regulators do not play a significant role in susceptibility and tolerance to this class of antibiotics.

[The role of natural environment in spreading of hantavirus--model of the correlation between host, pathogen and human infections]. / Rola srodowiska naturalnego w szerzeniu sie hantawirusów--model wspólzaleznosci pomiedzy gospodarzem, patogenem i zakazeniami ludzi.

The environmental changes caused by humans influence ecosystem and thus have significant impact on occurrence of emerging and re-emerging diseases. The hantavirus infection belong to the one of them. The aim of this paper was to present current knowledge about relationship between hantavirus, their natural host and the spread of the infection to people. Rodents constitute both the natural host of the hantaviruses and the reservoir of hantavirus for environment. Circulation of the virus in the rodent population is crucial to maintain the virus in the environment. The individual characteristics of rodents influence on risk of infection with hantavirus. However, this relationship is still unexplained. Risk of pathogen exposure often increases with age and behavioral differences associated with the sex of the susceptible individual. Mating behaviors seem to play an important role in the spread of the virus among rodents. Human incidence of hantavirus infection has in general been found to correlate to the population size of rodent host especially in the model of nephropathia epidemica (NE; a mild form of HFRS), Puumala virus (PUU) and bank voles. The occurrence of hantavirus infections in humans is assumed to rise as a secondary effect from altered population sizes of rodents in a changing environment due to e.g. mast years, forest fragmentation, global warming.

Correlation between temporomandibular dysfunction, disturbances of occlusion and gingival recession in a group of youth students.

UNLABELLED: The aim of this study was to investigate the relation between temporo-mandibular dysfunction (TMD), and disturbances of occlusion and gingival recession (GR) in a group of youth students. METHODS: The following measurements were performed: Anamnestic Index by Helkimo (AI), Diagnostic Index by Helkimo (DI), clinical evaluation of centric (CO) and excentric (EO) occlusion, clinical estimation of malocclusion and tooth malposition, anamnestic and clinical analysis of the occurrence of occlusal and non-occlusal parafunctions, anamnestic dysfunction of the vertebral column (ADVC), number of patients with GR > or = and/or < or = 2mm. RESULTS: Higher incidence of malposition teeth and ADVC were noted in a group of patients with CO disturbances. In the group of patients with disturbances of EO a significant higher number of patients with GR < or = 2 mm and a significant malposition of the teeth was observed. In the group of patients with clinical dysfunctions of TMD anamnestic dysfunction was more frequent. In the group of patients with GR a significant dependence on the age was proved. In this group there was also an increased occurrence of malposition of the teeth as well as malocclusions. The multifactor etiology of TMD and GR shows necessity of the more sharp diagnosis based on the movement system test.

Variation in predation risk and vole feeding behaviour: a field test of the risk allocation hypothesis.

Many prey animals experience temporal variation in the risk of predation and therefore face the problem of allocating their time between antipredator efforts and other activities like feeding and breeding. We investigated time allocation of prey animals that balanced predation risk and feeding opportunities. The predation risk allocation hypothesis predicts that animals should forage more in low- than in high-risk situations and that this difference should increase with an increasing attack ratio (i.e. difference between low- and high-risk situations) and proportion of time spent at high risk. To test these predictions we conducted a field test using bank voles ( Clethrionomys glareolus) as a prey and the least weasel ( Mustela nivalis nivalis) as a predator. The temporal pattern and intensity of predation risk were manipulated in large outdoor enclosures and the foraging effort and patch use of voles were measured by recording giving-up densities. We did not observe any variation in feeding effort due to changes in the level of risk or the proportion of time spent under high-risk conditions. The only significant effect was found when the attack ratio was altered: the foraging effort of voles was higher in the treatment with a low attack ratio than in the treatment with a high attack ratio. Thus the results did not support the predation risk allocation hypothesis and we question the applicability of the hypothesis to our study system. We argue that the deviation between the observed pattern of feeding behaviour of bank voles and that predicted by the predation risk allocation hypothesis was mostly due to the inability of voles to accurately assess the changes in the level of risk. However, we also emphasise the difficulties of testing hypotheses under outdoor conditions and with mammals capable of flexible behavioural patterns.