Tris(Imidazolyl) Dicopper(I) Complex and its Reactivity to Exert Catalytic Oxidation of Sterically Hindered Phenol Substrates via a [Cu2O]2+ Core

The Cu ion ligated with histidine residues is a common active site motif of various Cu-containing metalloenzymes exerting versatile catalytic oxidation reactions. Due to the scarce of structurally characterized biomimetic...

Amphipathic Dendritic Poly-peptides Carrier to Deliver Antisense Oligonucleotides Against Multi-drug Resistant Bacteria in Vitro and in Vivo

Background: Outbreaks of infection due to multidrug-resistant bacteria, especially gram-negative bacteria, have become a global health issue in both hospitals and communities. Antisense oligonucleotides (ASOs) based therapeutics hold a great promise for treating infections caused by multidrug-resistant bacteria. However, ASOs therapeutics are strangled because of its low cell penetration efficiency caused by the high molecular weight and hydrophilicity.Results: Here, we designed a series of dendritic poly-peptides (DPP1 to DPP12) to encapsulate ASOs to form DSPE-mPEG2000 decorated ASOs/DPP nanoparticles (DP-AD1 to DP-AD12) and observed that amphipathic DP-AD2, 3, 7 or 8 with a positive charge ≥ 8 showed great efficiency to deliver ASOs into bacteria, but only the two histidine residues contained DP-AD7 and DP-AD8 significantly inhibited the bacterial growth and the targeted gene expression of tested bacteria in vitro. DP-AD7anti-acpP remarkably increased the survival rate of septic mice infected by ESBLs-E. coli, exhibiting strong antibacterial effects in vivo.Conclusions: For the first time, we designed DPP as a potent carrier to deliver ASOs for combating MDR bacteria and demonstrated essential features, namely, amphipathicity, 8–10 positive charges, and 2 histidine residues, that are required for efficient DPP based delivery, and provide a novel approach for the development and research of the antisense antibacterial strategy.

PsaF is a membrane-localized pH sensor that regulates psaA expression in Y. pestis

The Yersinia pestis pH 6 antigen (PsaA) forms fimbria-like structures and is required for full virulence during bubonic plague. High temperature and low pH regulate PsaA production and while recent work has uncovered the molecular aspects of temperature control, the mechanisms underlying the unusual regulation by pH are poorly understood. Using defined growth conditions, we recently showed that high levels of PsaE and PsaF (two regulatory proteins required for expression of psaA ) are present at mildly acidic pH, but these levels are greatly reduced at neutral pH, resulting in low psaA expression. In prior work, the use of translational reporters suggested that pH had no impact on translation of psaE and psaF , but rather affected protein stability of PsaE and/or PsaF. Here, we investigated the pH-dependent post-translational mechanisms predicted to regulate PsaE and PsaF stability. Using antibodies that recognize the endogenous proteins, we showed that the amount of PsaE and PsaF is defined by a distinct pH threshold. Analysis of histidine residues in the periplasmic domain of PsaF suggested it functions as a pH-sensor and indicated that the presence of PsaF is important for PsaE stability. At neutral pH, when PsaF is absent, PsaE appears to be targeted for proteolytic degradation by regulated intramembrane proteolysis. Together, our work shows that Y. pestis utilizes PsaF as a pH sensor to control psaA expression by enhancing the stability of PsaE, an essential psaA regulatory protein. IMPORTANCE Yersinia pestis is a bacterial pathogen that causes bubonic plague in humans. As Y. pestis cycles between fleas and mammals, it senses the environment within each host to appropriately control gene expression. PsaA is a protein that forms fimbria-like structures and is required for virulence. High temperature and low pH together stimulate psaA transcription by increasing the levels of two essential integral membrane regulators, PsaE and PsaF. Histidine residues in the PsaF periplasmic domain enable it to function as a pH-sensor. In the absence of PsaF, PsaE (a DNA binding protein) appears to be targeted for proteolytic degradation, thus preventing expression of psaA . This work offers insight into mechanisms that bacteria use to sense pH and control virulence gene expression.

Synthetic Antimicrobial Peptides: III—Effect of Cationic Groups of Lysine, Arginine, and Histidine on Antimicrobial Activity of Peptides with a Linear Type of Amphipathicity

We have studied the antimicrobial and hemolytic activity of synthetic antimicrobial peptides (SAMPs), i.e., Arg9Phe2 (P1-Arg), Lys9Phe2 (P2-Lys), and His9Phe2 (P3-His), which have a “linear” type of amphipathicity and contain the cationic amino acid residues of arginine, lysine, or histidine. In this study, we have used various pathogenic microorganism strains of gram-negative bacteria (Pseudomonas aeruginosa, Escherichia coli, and Salmonella enterica), gram-positive bacteria (Staphylococcus aureus), and the conditionally pathogenic yeast fungus (Candida albicans). It has been shown that the replacement of the arginine residues by lysine or histidine residues in the tested SAMPs significantly degrades their antibacterial properties in the series: P1-Arg > P2-Lys $$ \gg $$P3-His. The cationic analog of SAMP, P1-Arg, has the highest antibacterial activity (MIC50 = 43–76 μM), while peptide P3-His does not exhibit this activity (MIC50 > 100 μM). The P1-Arg and P2-Lys peptides were 6–10 times more active against the opportunistic fungus C. albicans (MIC50 6.7 and 10.9 μM, respectively) and the P3-His peptide has 100-times increased antimycotic activity (MIC50 0.6 μM) compared with their effect on bacterial cells. All of the tested peptides with the linear type of amphipathicity and low hydrophobicity, i.e., P1-Arg, P2-Lys, and P3-His, that contain only two Phe residues regardless of the presence of cationic amino acids (Arg, Lys, or His) exhibit a relatively low hemolytic activity (not more than 4% hemolysis at 1000 μM peptide concentration). Thus, considering the same synthesis efficiency (56–63%) and approximately the same low toxicity of the tested SAMPs with a linear type of amphipathicity, it is recommended to use those that contain the cationic arginine or histidine residues to create antibacterial or antifungal peptide agents, respectively.

Covalent Histone Modification by an Electrophilic Derivative of the Anti-HIV Drug Nevirapine

Nevirapine (NVP), a non-nucleoside reverse transcriptase inhibitor widely used in combined antiretroviral therapy and to prevent mother-to-child transmission of the human immunodeficiency virus type 1, is associated with several adverse side effects. Using 12-mesyloxy-nevirapine, a model electrophile of the reactive metabolites derived from the NVP Phase I metabolite, 12-hydroxy-NVP, we demonstrate that the nucleophilic core and C-terminal residues of histones are targets for covalent adduct formation. We identified multiple NVP-modification sites at lysine (e.g., H2BK47, H4K32), histidine (e.g., H2BH110, H4H76), and serine (e.g., H2BS33) residues of the four histones using a mass spectrometry-based bottom-up proteomic analysis. In particular, H2BK47, H2BH110, H2AH83, and H4H76 were found to be potential hot spots for NVP incorporation. Notably, a remarkable selectivity to the imidazole ring of histidine was observed, with modification by NVP detected in three out of the 11 histidine residues of histones. This suggests that NVP-modified histidine residues of histones are prospective markers of the drug’s bioactivation and/or toxicity. Importantly, NVP-derived modifications were identified at sites known to determine chromatin structure (e.g., H4H76) or that can undergo multiple types of post-translational modifications (e.g., H2BK47, H4H76). These results open new insights into the molecular mechanisms of drug-induced adverse reactions.

Inhibitor Binding Modulates Protonation States in the Active Site of SARS-CoV-2 Main Protease

ABSTRACTThe main protease (3CL Mpro) from SARS-CoV-2, the virus that causes COVID-19, is an essential enzyme for viral replication with no human counterpart, making it an attractive drug target. Although drugs have been developed to inhibit the proteases from HIV, hepatitis C and other viruses, no such therapeutic is available to inhibit the main protease of SARS-CoV-2. To directly observe the protonation states in SARS-CoV-2 Mpro and to elucidate their importance in inhibitor binding, we determined the structure of the enzyme in complex with the α-ketoamide inhibitor telaprevir using neutron protein crystallography at near-physiological temperature. We compared protonation states in the inhibitor complex with those determined for a ligand-free neutron structure of Mpro. This comparison revealed that three active-site histidine residues (His41, His163 and His164) adapt to ligand binding, altering their protonation states to accommodate binding of telaprevir. We suggest that binding of other α-ketoamide inhibitors can lead to the same protonation state changes of the active site histidine residues. Thus, by studying the role of active site protonation changes induced by inhibitors we provide crucial insights to help guide rational drug design, allowing precise tailoring of inhibitors to manipulate the electrostatic environment of SARS-CoV-2 Mpro.