Search

A short peptide, FHHF-11, was designed to change stiffness as a function of pH due to changing degree of protonation of histidines. As pH changes in the physiologically relevant range, G' was measured at 0 Pa (pH 6) and 50,000 Pa (pH 8). This peptide-based hydrogel is antimicrobial and cytocompatible with skin cells (fibroblasts). It was demonstrated that the incorporation of unnatural AzAla tryptophan analog residue improves the antimicrobial properties of the hydrogel. The material developed can have a practical application and be a paradigm shift in the approach to wound treatment, and it will improve healing outcomes for millions of patients each year.

Streptococcus pyogenes (group A Streptococcus ) is a clinically important microbial pathogen that requires iron in order to proliferate. During infections, S. pyogenes uses the surface displayed Shr receptor to capture human hemoglobin (Hb) and acquires its iron-laden heme molecules. Through a poorly understood mechanism, Shr engages Hb via two structurally unique N-terminal Hb-interacting domains (HID1 and HID2) which facilitate heme transfer to proximal NEAr Transporter (NEAT) domains. Based on the results of X-ray crystallography, small angle X-ray scattering, NMR spectroscopy, native mass spectrometry, and heme transfer experiments, we propose that Shr utilizes a "cap and release" mechanism to gather heme from Hb. In the mechanism, Shr uses the HID1 and HID2 modules to preferentially recognize only heme-loaded forms of Hb by contacting the edges of its protoporphyrin rings. Heme transfer is enabled by significant receptor dynamics within the Shr-Hb complex which function to transiently uncap HID1 from the heme bound to Hb's β subunit, enabling the gated release of its relatively weakly bound heme molecule and subsequent capture by Shr's NEAT domains. These dynamics may maximize the efficiency of heme scavenging by S. pyogenes , enabling it to preferentially recognize and remove heme from only heme-loaded forms of Hb that contain iron.

Nonribosomal peptide synthetase heterocyclization (Cy) domains generate biologically important oxazoline/thiazoline groups found in natural products, including pharmaceuticals and virulence factors such as some siderophores. Cy domains catalyze consecutive condensation and cyclodehydration reactions, although the mechanism is unknown. To better understand Cy domain catalysis, here we report the crystal structure of the second Cy domain (Cy2) of yersiniabactin synthetase from the causative agent of the plague, Yersinia pestis. Our high-resolution structure of Cy2 adopts a conformation that enables exploration of interactions with the extended thiazoline-containing cyclodehydration intermediate and the acceptor carrier protein (CP) to which it is tethered. We also report complementary electrostatic interfaces between Cy2 and its donor CP that mediate donor binding. Finally, we explored domain flexibility through normal mode analysis and identified small-molecule fragment-binding sites that may inform future antibiotic design targeting Cy function. Our results suggest how CP binding may influence global Cy conformations, with consequences for active-site remodeling to facilitate the separate condensation and cyclodehydration steps as well as potential inhibitor development., Competing Interests: Conflict of interest The authors declare that they have no conflicts of interest with the contents of this article., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)

Pathogenic Staphylococcus aureus actively acquires iron from human hemoglobin (Hb) using the IsdH surface receptor. Heme extraction is mediated by a tri-domain unit within the receptor that contains its second (N2) and third (N3) NEAT domains joined by a helical linker domain. Extraction occurs within a dynamic complex, in which receptors engage each globin chain; the N2 domain tightly binds to Hb, while substantial inter-domain motions within the receptor enable its N3 domain to transiently distort the globin's heme pocket. Using molecular simulations coupled with Markov modeling, along with stopped-flow experiments to quantitatively measure heme transfer kinetics, we show that directed inter-domain motions within the receptor play a critical role in the extraction process. The directionality of N3 domain motion and the rate of heme extraction is controlled by amino acids within a short, flexible inter-domain tether that connects the N2 and linker domains. In the wild-type receptor directed motions originating from the tether enable the N3 domain to populate configurations capable of distorting Hb's pocket, whereas mutant receptors containing altered tethers are less able to adopt these conformers and capture heme slowly via indirect processes in which Hb first releases heme into the solvent. Thus, our results show inter-domain motions within the IsdH receptor play a critical role in its ability to extract heme from Hb and highlight the importance of directed motions by the short, unstructured, amino acid sequence connecting the domains in controlling the directionality and magnitude of these functionally important motions., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

hPG 80 (human circulating progastrin) is produced and released by cancer cells. We recently reported that hPG 80 is detected in the blood of patients with cancers from different origins, suggesting its potential utility for cancer detection. To accurately measure hPG 80 in the blood of patients, we developed the DxPG 80 test, a sandwich Enzyme-Linked Immunosorbent Assay (ELISA). This test quantifies hPG 80 in EDTA plasma samples. The analytical performances of the DxPG 80 test were evaluated using standard procedures and guidelines specific to ELISA technology. We showed high specificity for hPG 80 with no cross-reactivity with human glycine-extended gastrin (hG17-Gly), human carboxy-amidated gastrin (hG17-NH 2 ) or the CTFP (C-Terminus Flanking Peptide) and no interference with various endogenous or exogenous compounds. The test is linear between 0 and 50 pM hPG 80 (native or recombinant). We demonstrated a trueness of measurement, an accuracy and a variability of hPG 80 quantification with the DxPG 80 test below the 20% relative errors as recommended in the guidelines. The limit of detection of hPG 80 and the limit of quantification were calculated as 1 pM and 3.3 pM respectively. In conclusion, these results show the strong analytical performance of the DxPG 80 test to measure hPG 80 in blood samples.