Order controls disordered droplets: structure-function relationships in C9orf72-derived poly(PR)

Amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) have been thought as two distinct neurodegenerative diseases. However, recent genetic screening and careful investigations found the genetic and pathological overlap among these disorders. Hexanucleotide expansions in intron 1 of C9orf72 are a leading cause of familial ALS and familial FTD. These expansions facilitate the repeat-associated non-ATG initiated translation (RAN translation), producing five dipeptide repeat proteins (DRPs), including Arg-rich poly(PR: Pro-Arg) and poly-(GR: Gly-Arg) peptides. Arg is a positively charged, highly polar amino acid that facilitates interactions with anionic molecules such as nucleic acids and acidic amino acids via electrostatic forces and aromatic amino acids via cation-pi interaction, suggesting that Arg-rich DRPs underlie the pathophysiology of ALS via Arg-mediated molecular interactions. Arg-rich DRPs have also been reported to induce neurodegeneration in cellular and animal models via multiple mechanisms; however, it remains unclear why the Arg-rich DRPs exhibit such diverse toxic properties, because not all Arg-rich peptides are toxic. In this mini-review, we discuss the current understanding of the pathophysiology of Arg-rich C9orf72 DRPs and introduce recent findings on the role of Arg distribution as a determinant of the toxicity and its contribution to the pathogenesis of ALS.

Functional analysis of the polar amino acid in TatA transmembrane helix

The twin-arginine translocation (Tat) pathway utilizes the proton-motive force (PMF) to transport folded proteins across cytoplasmic membranes in bacteria and archaea, as well as across the thylakoid membrane in plants and the inner membrane in mitochondria. In most species, the minimal components required for Tat activity consist of three subunits, TatA, TatB, and TatC. Previous studies have shown that a polar amino acid is present at the N-terminus of the TatA transmembrane helix (TMH) across many different species. In order to systematically assess the functional importance of this polar amino acid in the TatA TMH in Escherichia coli, a complete set of 19-amino-acid substitutions was examined. Unexpectedly, although being preferred overall, our experiments suggest that the polar amino acid is not necessary for a functional TatA. Hydrophobicity and helix stabilizing properties of this polar amino acid were found to be highly correlated with the Tat activity. Specifically, change in charge status of the amino acid side chain due to pH resulted in a shift in hydrophobicity, which was demonstrated to impact the Tat transport activity. Furthermore, a four-residue motif at the N-terminus of the TatA TMH was identified by sequence alignment. Using a biochemical approach, the N-terminal motif was found to be functionally significant, with evidence indicating a potential role in the preference for utilizing different PMF components. Taken together, these findings yield new insights into the functionality of TatA and its potential role in the Tat transport mechanism.

Comparative assessment of the amino acids content of some legumes species in Southern Ukraine

The data on the composition and amount of amino acids have been analyzed in the raw materials of five legume species. All of them grow in Southern Ukrainian flora (Securigera varia (L.) Lassen, Vicia cracca L., Lupinus luteus L., Melilotus officinalis (L.) Pall., Melilotus albus Medic.) and may be used as a source of amino acids, especially essential, whose resource has to be replenished from the outside. Aim. We have studied and compared the amino acid profile of some species of the Ukrainian South Legumes, and used the multidimensional statistical cluster analysis to construction of histograms based on the amino acids content and composition of such plants as: Securigera varia (L.) Lassen, Vicia cracca L., Lupinus luteus L., Melilotus officinalis (L.) Pall., Melilotus albus Medic. Materials and methods. The raw materials were harvested at the South of Ukraine and were investigated by gas-liquid chromatography. The amino acid analyzer has been used after hydrochloric acid hydrolysis at elevated temperature. Results. 19 amino acids have been identified, of which nine are essential or partially interchangeable. The non-polar amino acid proline is in the lead in terms of quantity among the essential amino acids. Its amount was 6932 mg/100 g and the ability to accumulate it was noted in Melilotus officinalis (2276 mg/100 g). The smallest proline amount was found in Lupinus luteus (388 mg/100 g). The sulfur-containing non-polar amino acid methionine is in the smallest amount in the selected plants (506 mg/100 g). Our attention was drawn to the absence of the polar amino acid glutamine among the non-essential amino acids in some plants. Securigera varia, Vicia cracca, and Melilotus officinalis did not contain glutamine. In this subgroup, the polar aspartic acid was found in the highest amount (6824 mg/100 g) with the highest content in Vicia cracca and the lowest – in Melilotus albus (2660 mg/100 g and 385 mg/100 g, respectively). Conclusions. The analysis of the presence and number of amino acids was the basis for our multidimensional statistical cluster analysis and histograms of the presentation of the amino acid profile of the studied plant members of the family Fabaceae L. In constructing the dendrogram, three clusters were identified, and representatives of one genus (Melilotus L.) were attributed to different clusters which is significant for further chemosystematic studies.

New Anti SARS-Cov-2 Targets for Quinoline Derivatives Chloroquine and Hydroxychloroquine

The rapid spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has created a severe global health crisis. In this paper, we used docking and simulation methods to identify potential targets and the mechanism of action of chloroquine (CQ) and hydroxychloroquine (HCQ) against SARS-CoV-2. Our results showed that both CQ and HCQ influenced the functionality of the envelope (E) protein, necessary in the maturation processes of the virus, due to interactions that modify the flexibility of the protein structure. Furthermore, CQ and HCQ also influenced the proofreading and capping of viral RNA in SARS-CoV-2, performed by nsp10/nsp14 and nsp10/nsp16. In particular, HCQ demonstrated a better energy binding with the examined targets compared to CQ, probably due to the hydrogen bonding of the hydroxyl group of HCQ with polar amino acid residues.

Delving Deep into the Structural Aspects of the BPro28-BLys29 Exchange in Insulin Lispro: A Structural Biophysical Lesson

Insulin lispro was the first fast acting insulin analogue to obtain regulatory approval for therapeutic use. This article puts forward a novel biophysical mechanism where the net impact of the simple B28Pro-B29Lys exchange from regular insulin to insulin lispro is the establishment of a novel set of interfacial electrostatic interactions between Lys28 of insulin lispro and Asp12 of insulin receptor (IR). In addition, a set of structural analysis was presented in this article to further strengthen the binding of insulin lispro to IR, where two polar amino acid residues (Gln51 and Asn74 of insulin lispro) were put forward as two potential targets for site-directed mutagenesis of insulin lispro at its binding interface with IR.

Effect of polar amino acid incorporation on Fmoc-diphenylalanine-based tetrapeptides

The incorporation of polar amino acids into the Fmoc-FF motif yields tetrapeptide hydrogels whose biocompatibility in the gel state is inversely proportional to their biocompatibility in the solution state.

Vaccine antigen, Factor H binding protein, is typically a non-lipidated precursor that localises to the meningococcal surface by Slam

Meningococcal surface lipoprotein, Factor H binding protein (FHbp), is the sole antigen of the Trumenba vaccine (Pfizer) and one of four antigens of the Bexsero vaccine (GSK) targetingNeisseria meningitidisserogroup B isolates. Lipidation of FHbp is assumed to occur for all isolates and its surface localisation is conducted by surface lipoprotein assembly modulator, Slam.We show in 91% of a collection of UK isolates (1742/1895) non-synonymous single nucleotide polymorphisms (SNPs) in the signal peptide of FHbp. A single SNP, common to all, alters a polar amino acid that abolishes processing, including lipidation and signal peptide cleavage. Rather than the toxic accumulation of the precursor in the periplasm as expected from disrupting the canonical processing pathway, remarkably the FHbp precursor is translocated to the outer membrane and surface-localised by Slam. Thus we show Slam is not lipoprotein-specific. In a panel of isolates expressing precursor FHbp at the surface, we investigated their binding to human factor H and their susceptibility to antibody-mediated killing. Our findings have implications for Trumenba and Bexsero and provide key insights for lipoprotein-based vaccines in development.