Chemical imitation of yeast fermentation by the drosophilid-pollinated deceptive trap-flower Aristolochia baetica (Aristolochiaceae).

Deceptive flowers, unlike in mutualistic pollination systems, mislead their pollinators by advertising rewards which ultimately are not provided. Although our understanding of deceptive pollination systems increased in recent years, the attractive signals and deceptive strategies in the majority of species remain unknown. This is also true for the genus Aristolochia, famous for its deceptive and fly-pollinated trap flowers.

Quantitative and functional characterisation of extracellular vesicles after passive loading with hydrophobic or cholesterol-tagged small molecules.

Extracellular vesicles (EVs) are nanosized intercellular messengers that bear enormous application potential as biological drug delivery vehicles. Much progress has been made for loading or decorating EVs with proteins, peptides or RNAs using genetically engineered donor cells, but post-isolation loading with synthetic drugs and using EVs from natural sources remains challenging. In particular, quantitative and unambiguous data assessing whether and how small molecules associate with EVs versus other components in the samples are still lacking.

Stereochemistry-Driven Interactions of α,γ-Peptide Ligands with the Neuropeptide Y Y-Receptor.

The G-protein-coupled Y-receptor (YR) and its endogenous ligand, pancreatic polypeptide (PP), suppress appetite in response to food intake and, thus, are attractive drug targets for body-weight control. The C-terminus of human PP (hPP), T-R-P-R-Y-, penetrates deep into the binding pocket with its tyrosine-amide and di-arginine motif. Here, we present two C-terminally amidated α,γ-hexapeptides (/) with sequence -R-γ-CBAA-R-L-R-Y-, where γ-CBAA is the (1,2,3)-configured 2-(aminomethyl)-3-phenylcyclobutanecarboxyl moiety () or its mirror image ().

Conformational Control of Fast Asparagine Deamidation in a Norovirus Capsid Protein.

Accelerated spontaneous deamidation of asparagine 373 and subsequent conversion into an isoaspartate has been shown to attenuate the binding of histo blood group antigens (HBGAs) to the protruding domain (P-domain) of the capsid protein of a prevalent norovirus strain (GII.4). Here, we link an unusual backbone conformation of asparagine 373 to its fast site-specific deamidation.

EVAnalyzer: High content imaging for rigorous characterisation of single extracellular vesicles using standard laboratory equipment and a new open-source ImageJ/Fiji plugin.

Extracellular vesicle (EV) research increasingly demands for quantitative characterisation at the single vesicle level to address heterogeneity and complexity of EV subpopulations. Emerging, commercialised technologies for single EV analysis based on, for example, imaging flow cytometry or imaging after capture on chips generally require dedicated instrumentation and proprietary software not readily accessible to every lab. This limits their implementation for routine EV characterisation in the rapidly growing EV field.

Backbone distortions in lactam-bridged helical peptides.

Side-chain-to-side-chain cyclization is frequently used to stabilize the α-helical conformation of short peptides. In a previous study, we incorporated a lactam bridge between the side chains of Lys-i and Asp-i+4 in the nonapeptide 1Y, cyclo-(2,6)-(Ac-VKRLQDLQY-NH ), an artificial ligand of the inhibitor of DNA binding and cell differentiation (ID) protein with antiproliferative activity on cancer cells. Herein, we show that only the cyclized five-residue segment adopts a helical turn whereas the C-terminal residues remain flexible.

A Conformationally Stable Acyclic β-Hairpin Scaffold Tolerating the Incorporation of Poorly β-Sheet-Prone Amino Acids.

The β-hairpin is a structural element of native proteins, but it is also a useful artificial scaffold for finding lead compounds to convert into peptidomimetics or non-peptide structures for drug discovery. Since linear peptides are synthetically more easily accessible than cyclic ones, but are structurally less well-defined, we propose XWXWXpPXK(/R)X(R) as an acyclic but still rigid β-hairpin scaffold that is robust enough to accommodate different types of side chains, regardless of the secondary-structure propensity of the X residues. The high conformational stability of the scaffold results from tight contacts between cross-strand cationic and aromatic side chains, combined with the strong tendency of the d-Pro-l-Pro dipeptide to induce a type II' β-turn.

The Peptide Ligase Activity of Human Legumain Depends on Fold Stabilization and Balanced Substrate Affinities.

Protein modification by enzymatic breaking and forming of peptide bonds significantly expands the repertoire of genetically encoded protein sequences. The dual protease-ligase legumain exerts the two opposing activities within a single protein scaffold. Primarily localized to the endolysosomal system, legumain represents a key enzyme in the generation of antigenic peptides for subsequent presentation on the MHCII complex.

Detecting aspartate isomerization and backbone cleavage after aspartate in intact proteins by NMR spectroscopy.

The monitoring of non-enzymatic post-translational modifications (PTMs) in therapeutic proteins is important to ensure drug safety and efficacy. Together with methionine and asparagine, aspartic acid (Asp) is very sensitive to spontaneous alterations. In particular, Asp residues can undergo isomerization and peptide-bond hydrolysis, especially when embedded in sequence motifs that are prone to succinimide formation or when followed by proline (Pro).

A novel FRET peptide assay reveals efficient Helicobacter pylori HtrA inhibition through zinc and copper binding.

Helicobacter pylori (H. pylori) secretes the chaperone and serine protease high temperature requirement A (HtrA) that cleaves gastric epithelial cell surface proteins to disrupt the epithelial integrity and barrier function. First inhibitory lead structures have demonstrated the essential role of HtrA in H.

Identification and Quantification of Oxidation Products in Full-Length Biotherapeutic Antibodies by NMR Spectroscopy.

Therapeutic proteins are an indispensable class of drugs and often therapeutics of last resort. They are sensitive to oxidation, which is of critical concern, because it can affect drug safety and efficacy. Protein oxidation, with methionine and tryptophan as the most susceptible moieties, is mainly monitored by HPLC-MS techniques.

Unambiguous Identification of Pyroglutamate in Full-Length Biopharmaceutical Monoclonal Antibodies by NMR Spectroscopy.

Biotherapeutic proteins are an indispensable class of pharmaceuticals that present a high degree of structural complexity and are prone to chemical modifications during production, processing, and storage, which have to be tightly controlled. Pyroglutamate (pGlu), a cyclization product of N-terminal Gln or Glu residues, is a widespread post-translational modification in proteins, including monoclonal antibodies (mAbs). The unambiguous identification and quantification of this modification in proteins is challenging, since the mass difference of -17 Da or -18 Da, when formed from Gln or Glu, respectively, is not unique.

An explorative study towards the chemical synthesis of the immunoglobulin G1 Fc CH3 domain.

Monoclonal antibodies, fusion proteins including the immunoglobulin fragment c (Ig Fc) CH2-CH3 domains, and engineered antibodies are prominent representatives of an important class of drugs and drug candidates, which are referred to as biotherapeutics or biopharmaceuticals. These recombinant proteins are highly heterogeneous due to their glycosylation pattern. In addition, enzyme-independent reactions, like deamidation, dehydration, and oxidation of sensitive side chains, may contribute to their heterogeneity in a minor amount.